Climate Change and Occupational Heat Strain Among Women Workers: A Systematic Review

Abstract

Climate change increases heat stress exposure and occupational heat strain in tropical and subtropical regions with generally hot–humid climate conditions. The present systematic review was conducted to assess the effect of climate change on occupational heat strain among women workers. In this study, three main databases (PubMed, Scopus, and Web of Science) were searched to find relevant literature on climate change and its effects using subject headings and appropriate MeSh terms. This article has been written according to the PRISMA checklist. A total of 6,176 studies were identified for screening and 13 studies were eligible for data extraction. Scientific evidence reveals that there is an imprecise but positive relationship between climate change and occupational heat strain regarding women workers. Some complications associated with occupational heat strain among women workers include fatigue, discomfort, dehydration, reduced brain function, and loss of concentration. Climate change can lead to an increase in the occurrence of heat-related illnesses and the levels of injury risk. In addition, its adverse health effects on women workers are mentioned. This systematic study identifies key priorities for action to better characterize and understand how occupational heat strain among women workers may be associated with climate change events. Strong evidence indicates that climate change will continue to cause occupational heat strain among women workers. It is essential to implement preventive measures considering multidisciplinary strategies to reduce the adverse effects of climate change on women workers health in hot weather settings. This can limit the health risks and negative effects of climate change.

INTRODUCTION

Occupational heat exposure and heat strain responses due to climate change have emerged as a threat to the health, safety, and social well-being of the diverse working population in the world. This is especially true for people working in settings that cannot be or are not cooled by air conditioning, electric fans, or other cooling technical methods.[1,2,3,4,5,6] Evidence has also shown that higher ambient temperature due to climate change and increased exposure to hot and high humidity environments may induce moderate-to-high heat strain, accidents, and injuries among the women working population, especially during hot seasons.[4] Several important factors can affect heat strain including age, sex, body mass index (BMI), medical conditions, and type of occupation.[7] Physiological and perceptual responses, anthropometrical, and individual parameters are the most important factors that affect the thermoregulation of men and women working in hot–humid weather conditions. Different factors affect thermoregulation in both men and women, including anthropometric specifications, specific physiologic factors in women (sex hormones, menstrual cycle, and menopausal transition), socio-psychology, aerobic fitness, and physical characteristics.[8,9,10] Women working in hot workplaces including greenhouse settings, hospital laundry, agriculture industry, and bakeries, are exposed to numerous health hazards that can lead to heat-related illnesses such as heat cramps, heat exhaustion, heat stroke, and death. Even the mildest hazards can increase the risk of accidents, injuries, and mental health effects in workplaces among thousands of workers every year.[7,11,12,13,14,15,16] Demographic variables including socio-economic factors such as occupational status, marital status, self-rated economic status, educational background, and the number of children; lifestyle factors such as physical activity, hours of sleep, smoking; psychological factors such as pregnancy situation, metabolic heat production and menstrual cycle; type of clothing; and BMI in women in hot and humid environments can also affect thermoregulation parameters such as core body temperature, skin temperature, physical characteristics, mental workload, fluid balance, thermal stress, and sweat rate.[8,9,17] These variables will worsen with climate change, demonstrating the need to identify the effects of climate change on occupational heat strain and create solutions and suggestions to provide safe and healthy workplaces for women now and in the future.[13] Due to a lot of physiological and perceptual differences between men and women regarding heat exposure, it is necessary to summarize the findings of published studies, and ultimately provide suggestions for heat strain reduction, adaptations, and further research directions to identify the effects of climate change on employed women. Although the health effects of occupational heat exposure have been widely examined, there has been little discussion about the effects of occupational heat stress on women workers’ health. Therefore, the aim of this systematic review is to show the effect of climate change on occupational heat strain among women workers.

MATERIALS AND METHODS

Bibliography search strategy

Our systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).[18]

Databases such as PubMed, Scopus, and Web of Science were searched for articles published between 2000 and October 2019. All search terms related to “climate change” were found by the PubMed Mesh system, as were some synonyms (as suggested by a specialist) of terms in combination with “heat strain.” The search syntax was conducted using keywords and synonyms that were searched in the title, abstract, or keyword fields in databases. The Number Need to Read (NNR) was about 13 in the Web of Science search. Finally, to find more relevant documents in this field, according to the SCOPUS search results, three journals that had the most related included studies searched as key journals; these key journals were “International Journal of Biometeorology,” “the Journal of Thermal Biology,” and “PLOS One.” To find more relevant studies, the reference list of included studies was also investigated. Databases were examined by following search syntaxes to find relevant studies:

PubMed: (“heat strain”[tiab] OR “heat cramp”[tiab] OR (heat[tiab] AND cramp[tiab]) OR “heat stroke”[tiab] OR “heat stress”[tiab]) AND (“climate change*”[tiab] OR (climate[tiab] AND change[tiab]) OR “extreme weather”[tiab] OR “extreme heat”[tiab]).

Eligibility criteria

The “PICO” strategy for systematic exploratory review was: P (individuals), I (climate change), C (occupational heat strain), and O (heat strain reduction).

Papers were included if they were (a) peer-reviewed articles; (b) conducted on women workers; (c) about climate change, and if they (d) outlined the impacts of climate change on heat strain; (e) consisted of comparisons between countries or workplaces.

Exclusion criteria were as follows: (a) articles about heat-related mortality and morbidity among the general population from different countries; (b) effects on the elderly, or those which only outlined impacts on men and children’s health; (c) evaluated the effect of climate change on animals, biological (flora, fauna) and physical (soil, land, water, climate) systems; (e) full-text articles or conference papers that were unavailable.

Study selection

All the examined research was transferred to EndNote, and duplicated studies were removed. A researcher (PH) screened the literature according to the title and the abstract, and two researchers (PH and AH) selected studies and extracted information from eligible studies independently by reviewing the full text. Disagreements between the two reviewers concerning study inclusion or exclusion were resolved by research team consensus. More disagreements were discussed and resolved throughout the authors’ group discussions and consensus.

Data extraction and quality assessment

Two independent reviewers (PH and AH) assessed the quality of included studies using a 16-item, quality assessment tool (QATSDD) checklist. This tool shows good reliability and validity for use in the quality assessment in a diversity of studies.[19] Any disagreement between reviewers was resolved by research group consensus.

RESULTS

Search results

A detailed list of all searches is presented in the flow diagram in Figure 1. The initial electronic search yielded 6,179 articles. Through hand-searching of key journals, two relevant articles were found. However, no studies were included based on our eligibility criteria after the full-text investigation.

Figure 1.

Flow diagram of the screening process of included studies for the systematic review of the effect of cooling vest on physiological and perceptual response chart for study selection

In total, 6,138 articles were excluded after the title and abstract screening, and 64 articles were considered eligible for full-text evaluation. Subsequently, 12 articles were included in the qualitative analysis, and 1 study was added through hand-searching. Table 1 summarizes the characteristics of the included studies. Table 2 indicates which risk factors can be expected from climate change, such as environmental, organizational, and individual factors. Table 3 indicates which suggestions can be expected to reduce climate change effects.

Table 1.

Characteristics of included studies examining climate change and occupational heat strain among women workers

Author/year and country	Type of document	Occupation	Main health impacts related to climate change	Outcome	Quality rating
Jianjun et al., 2016 (Australia) (Xiang, Hansen et al. 2016)[20]	Cross-sectional	Workers with a high risk of workplace heat exposure	Heat-related illnesses, Injuries, and Deaths.	Developing workers’ heat risk awareness and refining current heat prevention strategies in a warming climate should be done.	34
Jianjun et al., 2014 (Xiang, Bi et al. 2014)[21]	Review	Manual workers	Cardiovascular diseases, Mental health problems, Chronic kidney diseases, Dehydration, Fatigue, Irritability, Lethargy, Impaired judgment, Vigilance decrement, Loss of dexterity, coordination and concentration, Feeling thirst, Waking up early due to hot conditions, Impatience, Headache, Dizziness, Heat stroke, Morbidity, Mortality, High in blood lactate levels, Longer recovery time, Increase in heart rate, Increase in core temperature, Increase of anxiety level, Increase of risk of injury, Dyslipidemia, Digestive diseases, Elevate in blood pressure, and Elevate in urine gravity.	Development of more studies for identifying manual workers’ heat risk and psychologically affected should be done by climate change.	24
Lukman et al., 2019 (Nigeria) (Sadiq, Hashim et al. 2019)[22]	Cross-sectional	Maize farmers	Heavy sweating, Tiredness, Dizziness, Headache, Weakness, Difficulty in breathing, Unconsciousness, Heat rash, Elevated body temperature, Rapid pulse, Nausea/vomiting, Muscle cramp, Fainting, Hot- dry skin, Pricking sensation, Fatigue, Heat syncope, Heat stroke, Heat exhaustion, and Reduced work productivity.	Maize farmers in hot tropical countries are at risk of heat exhaustion which decreased their productivity.	24
Bandana et al., 2013 (Nepal) (Pradhan, Shrestha et al. 2013)[23]	Case study	Different jobs	Faint, Tension, Irritation, Laziness, Dehydration, Giddiness, Heat rash, Diarrhea, Typhoid, Eye infection, Appetite loss, Urinary tract infection, Unconsciousness, Hypertension, Fever, Morbidity, Mortality, Heat cramps, Heat exhaustion, and Discomfort.	Climate change may be caused by increasing negatively on workers’ health effects and productivity loss.	25
Tjaša et al., 2019 (Slovenia and Greece) (Pogacar, Znidarsic et al. 2019)[24]	Cross-sectional	Outdoor workers	Thirst, Excessive sweating, Heat exhaustion, Headache, Tiredness, Dizziness, Confusion, Enhanced stress, Prickly heat, Fainting, Nausea/vomiting, Heat cramps, and Heat stroke, Work-related injury, Diarrhea, Irritability, Hallucination, Loss of coordination, Weakness, and Kidney disease.	Climate change can negatively impact productivity and well-being and endanger health.	23
Victor et al., 2019 (Ghana) (Nunfam, Van Etten et al. 2019)[25]	Cross-sectional	Supervisory personnel and other stakeholders	Heat-related illnesses, Injury, Deaths, Excessive sweating, Headache, Heat exhaustion/tiredness, Heat rash, Heat syncope(fainting), Burns from hot objects/surfaces, Falls, trips, and slips due to dizziness, fainting, and fatigue, Being hit by an object, Loss of grip and controls due to sweaty hands, Dehydration, Heat stress, and Heatstroke.	Supervisors’ climate change risks perception was adequate, and mining workers’ occupational heat stress risks experience heat-related illness and minor injuries.	28
Victor et al., 2019 (Ghana) (Nunfam, Oosthuizen et al. 2019)[26]	Cross-sectional	Mining workers	Excessive sweating, Headaches, Heat exhaustion/tiredness, Heat cramp, Heat rash, Heat syncope (fainting), Admitted to the hospital due to heat stroke, Heat-related injury experience, Burns from the sun, Burns from hot objects/surfaces, Falls, trips, and slips due to dizziness, fainting, and fatigue, Loss of grip and controls due to sweaty hands, Being hit by objects, Hitting objects, Reduce in productive capacity, Disrupt in social well-being, and morbidity.	Workers’ climate change risk perception, as confirmed by trends in climate data, was reasonable.	29
Haruna et al., 2019 (Africa) (Moda, Leal et al. 2019)[27]	Systematic review	Outdoor workers	Discomfort, Heat cramp, Respiratory difficulties, Heat stroke, Deaths, Cardiovascular systems, Increased heart rate, Increased core body temperature, Increased sweating, Fluctuation of blood flow towards the skin, Dehydration, Impairment of mental and physical performance, Kidney Disease, Fatigue, Increase morbidity and fatality, Heat-related illnesses, Nausea or vomiting, Painful muscular spasms, Confusion, Dizziness, or fainting, Hot- dry skin, Heat strain, and Chemical poisoning.	Climate change can negatively impact outdoor workers’ productivity and occupational safety in tropical developing countries.	33
Karin et al., 2013 (Developing countries) (Lundgren, Kuklane et al. 2013)[28]	Review	Working population	Mortality, Morbidity, Heat exhaustion, Heat stroke, Increase in core body temperature, Increase in skin blood flow, Increase in sweating, Dehydration, Injuries, Heat fatigue, Higher burden of respiratory, Higher burden of cardiovascular diseases, Cataract, Kidney failure, Weak of the immune system , High blood flow, Effect on reaction time, Effect on tracking and vigilance, Effect on memory and mathematical calculations, Discomfort, Fatigue, Psychological strain, Stress, Physical health problems, Mental problems, and Chronic kidney disease.	Climate change can negatively impact the working population’s health status and reduce work productivity.	18
Chuansi et al., 2018 (Gao, Kuklane et al. 2018)[29]	Review	N/A	Physical and cognitive performance reduction, Increase in heart rate, Discomfort, Increase in sweat rate, Increase in skin temperatures, and Increase in core body temperature	Prevalence of negative impact on occupational health and public health risk in future work.	32
Raul et al., 2016 (Ecuador) (Arjona, Pineiros et al. 2016)[30]	Review	Agricultural workers	Morbidity and mortality, Dehydration, Revival syndrome, Excessive sweating, and Heat cramp.	Increasing prevalence of UV radiation and heat stress-related illnesses in agricultural workers worldwide due to global air pollution and temperature.	23
Habibollah et al., 2013 (Iran) (Dehghan, Habibi et al. 2013)[10]	Cross-sectional	Different jobs	Fatigue, Heat stroke, Discomfort, Intensity of thirst, and Increase in sweat rate.	There is a questionnaire for preliminary assessment of women’s heat strain in hot-dry climate conditions of Iran.	29

Table 2.

Risk factors that may increase susceptibility to climate-related occupational hazards

Domain	Sub-domain	Factors
Individual	Demographic factors	Age (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019,[24] Sadiq, Hashim et al. 2019[22])
		Sex (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019,[24] Sadiq, Hashim et al. 2019[22])
		Genetic susceptibility (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Arjona, Pineiros et al. 2016[30])
		BMI (Schulte and Chun 2009,[31] Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28]
		Xiang, Bi et al. 2014,[21] Gao, Kuklane et al. 2018,[29] Nunfam, Van Etten et al. 2019,[25] Sadiq, Hashim et al. 2019[22])
		Individual factors (Lundgren, Kuklane et al. 2013[28])
		Education level (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Xiang, Hansen et al. 2016,[20] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019,[24] Sadiq, Hashim et al. 2019[22])
		Years of experience (Dehghan, Habibi et al. 2013,[10] Nunfam, Oosthuizen et al. 2019,[26] Sadiq,
		Hashim et al. 2019[22])
		Number of children (Dehghan, Habibi et al. 2013,[10] Sadiq, Hashim et al. 2019[22])
		Marital status (Sadiq, Hashim et al. 2019[22])
		Ethnicity (Lundgren, Kuklane et al. 2013,[28] Xiang, Bi et al. 2014[21])
		Cultural aspects (Lundgren, Kuklane et al. 2013[28])
	Physical fitness	Obesity (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Physical disability (Pogacar, Znidarsic et al. 2019[24])
		Frail (Gao, Kuklane et al. 2018[29])
		Aerobic capacity (Lundgren, Kuklane et al. 2013,[28] Xiang, Bi et al. 2014,[21] Gao, Kuklane et al. 2018[29])
		Body fat content (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Fitness level (Xiang, Bi et al. 2014[21])
	Physical health	Medical conditions (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Heart disease (Pogacar, Znidarsic et al. 2019[24])
		Lung disease (Lundgren, Kuklane et al. 2013,[28] Pogacar, Znidarsic et al. 2019[24])
		Pregnancy (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Moda, Leal et al. 2019[27])
		Cardiovascular disease (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Chronic disease (Gao, Kuklane et al. 2018,[29] Pogacar, Znidarsic et al. 2019[24])
		Health status (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Kidney disease (Arjona, Pineiros et al. 2016[30])
		Infection disease (Arjona, Pineiros et al. 2016[30])
		Disabilities (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018[29])
		The sensitivity of individuals (Gao, Kuklane et al. 2018[29])
		Dehydration or poorly hydrated (Dehghan, Habibi et al. 2013,[10] Gao, Kuklane et al. 2018,[29]
		Pogacar, Znidarsic et al. 2019[24])
		Skin temperature (Gao, Kuklane et al. 2018[29])
		Core body temperature (Gao, Kuklane et al. 2018[29])
		Sustained sweating (Dehghan, Habibi et al. 2013[10])
		Insufficient in sweat rate (Lundgren, Kuklane et al. 2013,[28] Moda, Leal et al. 2019[27])
		Heat illness history or injury (Dehghan, Habibi et al. 2013,[10] Xiang, Hansen et al. 2016[20])
		Skin problem (Lundgren, Kuklane et al. 2013[28])
		Liver problem (Lundgren, Kuklane et al. 2013[28])
		Reproductive hormones (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Menstrual phase (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Breast-feeding (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Malnutrition (Lundgren, Kuklane et al. 2013[28])
		Immunologic status (Schulte and Chun 2009[31])
		Oral temperature (Dehghan, Habibi et al. 2013[10])
	Mental health	Mental illness (Pogacar, Znidarsic et al. 2019[24])
		Cognitive impairment (Pogacar, Znidarsic et al. 2019[24])
		Psychiatric illnesses (Lundgren, Kuklane et al. 2013[28])
	Behavioral	Use of PPE (Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Golbabaei, Heydari et al. 2020[32])
		Physical intensity (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Arjona, Pineiros et al. 2016,[30] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26]
		Pogacar, Znidarsic et al. 2019,[24] Sadiq, Hashim et al. 2019[22])
		Degree of acclimatization (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Xiang,
		Bi et al. 2014,[21] Gao, Kuklane et al. 2018,[29] Nunfam, Van Etten et al. 2019[25])
		Metabolic rate (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019[27])
		Insufficient fluid replacement (Dehghan, Habibi et al. 2013,[10] Xiang, Hansen et al. 2016,[20] Moda, Leal et al. 2019[27])
	Life style	Drugs and alcohol exposure (Lundgren, Kuklane et al. 2013,[28] Arjona, Pineiros et al. 2016,[30]
		Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Smoking (Lundgren, Kuklane et al. 2013[28])
		Nephrotoxic drugs (Arjona, Pineiros et al. 2016[30])
		Excess use of NSAIDs (Arjona, Pineiros et al. 2016[30])
		Caffeine consumption habit (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013[28])
		Use of medical drugs (Dehghan, Habibi et al. 2013[10])
Environmental	Work station	Ergonomic risks (Body posture, Movement, Confined space, etc.) (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pogacar, Znidarsic et al. 2019[24])
	Climatic Condition
	Tropical	Environmental conditions (Air temperature, Heatwave, Extreme weather, etc.) (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019,[24] Sadiq, Hashim et al. 2019[22])
		Air pollution (Lundgren, Kuklane et al. 2013,[28] Moradi, Sadighzadeh et al. 2013,[33] Moda, Leal et al. 2019[27])
		Heat radiation (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Moda, Leal et al. 2019[27])
		Relative humidity (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Dry Air Temperature (Dehghan, Habibi et al. 2013,[10] Tan, Cheong et al. 2021[34])
		Solar radiation (Dehghan, Habibi et al. 2013,[10] Habibi, Dehghan et al. 2017,[35] Habibi, Moradi et al. 2021[36])
	Dry	Solar radiation (Dehghan, Habibi et al. 2013[10])
		Heat radiation (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Moda, Leal et al. 2019[27])
		Air pollution (Lundgren, Kuklane et al. 2013,[28] Moradi, Sadighzadeh et al. 2013,[33] Moda, Leal et al. 2019[27])
		Ambient water vapor pressure (Roberts 1943[37])
	Temperate	Atmospheric pressure (Pradhan, Shrestha et al. 2013[23])
		Air pollution (Lundgren, Kuklane et al. 2013,[28] Moradi, Sadighzadeh et al. 2013,[33] Moda, Leal et al. 2019[27])
		Wind speed (Dehghan, Habibi et al. 2013,[10] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019[26])
		Solar radiation (Dehghan, Habibi et al. 2013[10])
	Continental	Relative humidity (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Air pollution (Lundgren, Kuklane et al. 2013,[28] Moradi, Sadighzadeh et al. 2013,[33] Moda, Leal et al. 2019[27])
		Acclimatization from warm-to-cold (De Freitas and Grigorieva 2015[38])
		Air temperature (Dehghan, Habibi et al. 2013,[10] De Freitas and Grigorieva 2015[38])
	Polar	Air movement (Dehghan, Habibi et al. 2013,[10] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019[26])
		Air pollution (Lundgren, Kuklane et al. 2013,[28] Moradi, Sadighzadeh et al. 2013,[33] Moda, Leal et al. 2019[27])
		Ambient water vapor pressure (Roberts 1943[37])
		Relative humidity (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Air temperature (Roberts 1943[37])
Organizational	Job-related	Income (Lundgren, Kuklane et al. 2013,[28] Sadiq, Hashim et al. 2019[22])
		Individual work habits (Xiang, Hansen et al. 2016[20])
		Work characteristics (Task complexity, Concentration, etc.) (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
		Poor working conditions (Arjona, Pineiros et al. 2016[30])
		Physical demands of jobs (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Gao, Kuklane et al. 2018,[29] Nunfam, Oosthuizen et al. 2019,[26]
		Nunfam, Van Etten et al. 2019[25])
		Working around heat sources (Dehghan, Habibi et al. 2013,[10] Xiang, Bi et al. 2014,[21] Arjona, Pineiros et al. 2016,[30] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
		Outdoors work(Solar radiation) (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
		Exposure to noise (Dehghan, Habibi et al. 2013,[10] Moradi, Omidi et al. 2019[39])
	Equipment	Clothing properties( Protective clothing, Color of clothing and Size of clothing) (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
	Facilities	Poorly or no air-conditioning or fans and distance from the cool restroom (Dehghan, Habibi et al. 2013,[10] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Moda, Leal et al. 2019,[27] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
		Poor access to safe drinking water or distance from drinking water location (Dehghan, Habibi et al. 2013[10])
		Absence of trees and vegetation in urban areas (Moda, Leal et al. 2019[27])
	Management	Work shift (Dehghan, Habibi et al. 2013,[10] Nunfam, Oosthuizen et al. 2019[26])
		Time spent indoors/outdoors (Dehghan, Habibi et al. 2013,[10] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Nunfam, Van Etten et al. 2019[25])
		Duration of break/rest hours (Dehghan, Habibi et al. 2013,[10] Xiang, Bi et al. 2014,[21] Nunfam, Oosthuizen et al. 2019[26])
		Inadequate prevention and control policies (Moda, Leal et al. 2019[27])
		Country level, low- and middle-income countries(LMICs) (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Moda, Leal et al. 2019,[27] Nunfam, Van Etten et al. 2019[25])
		Inadequate awareness of heat stress risks, training, and skills (Gao, Kuklane et al. 2018,[29] Nunfam, Van Etten et al. 2019[25])
		Years of OHS work experience (Nunfam, Van Etten et al. 2019[25])
		Fewer drinking rest breaks (Dehghan, Habibi et al. 2013[10])
		Lack of occupational health and safety programs (Xiang, Bi et al. 2014[21])

Table 3.

Measures for controlling climate change and occupational heat strain among women workers

Domain	Preventive recommendations
Managerial control	Education and training (Schulte and Chun 2009,[31] Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24]) Use and improving guidelines, risk assessment, indices, and standards (Lundgren, Kuklane et al. 2013,[28] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
	Use of preventive strategies in a warm climate (Xiang, Hansen et al. 2016[20])
	Work/rest cycle (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
	Adequate supply of clean drinking water and electrolyte drinks near the workstations and in short distances (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Hansen et al. 2016,[20] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
	“Stopping work” in exposure to hot temperature (>40°C) (Xiang, Hansen et al. 2016[20])
	Responding to early symptoms (Xiang, Hansen et al. 2016[20])
	Policy and regulation implementation (Lundgren, Kuklane et al. 2013,[28] Xiang, Hansen et al. 2016[20])
	Selection criteria when recruiting workers(Lundgren, Kuklane et al. 2013,[28] Xiang, Bi et al. 2014,[21] Gao, Kuklane et al. 2018[29])
	-Temporary tents for rest (Xiang, Bi et al. 2014[21])
	Global “Hothaps” program (Pradhan, Shrestha et al. 2013,[23] Pogacar, Znidarsic et al. 2019[24])
	Rearrangement of work tasks to cooler parts of the day and season (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Schulte, Bhattacharya et al. 2016,[13] Nunfam, Oosthuizen et al. 2019[26])
	Use of appropriate PPE (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013[23])
	Identify new climate models (Gao, Kuklane et al. 2018[29])
	Proper a cold rest places (Pradhan, Shrestha et al. 2013,[23] Pogacar, Znidarsic et al. 2019[24])
	Keeping trees or other creators of shade (roof or walls) (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
	Avoiding direct sunshine (Gao, Kuklane et al. 2018[29])
	Medical monitoring (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018[29])
	Compensation, social protection and payment per hour (Nunfam, Oosthuizen et al. 2019[26])
	Assessment of climate change impact (Gao, Kuklane et al. 2018[29])
	Nutritional status (Lundgren, Kuklane et al. 2013[28])
	Widespread precautious work (Lundgren, Kuklane et al. 2013[28])
Engineering control	Cooling, air conditioning, and electric fans (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Bi et al. 2014,[21] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019[25])
	Reduce greenhouse gas emissions (Lundgren, Kuklane et al. 2013[28])
	Heat-shield project (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018,[29] Pogacar, Znidarsic et al. 2019[24])
	Early warning and emergency response systems (Lundgren, Kuklane et al. 2013[28])
	Eliminating or reduction heat sources (Arjona, Pineiros et al. 2016,[30] Gao, Kuklane et al. 2018,[29] Nunfam, Oosthuizen et al. 2019[26])
	Design and insulation of workplace buildings (Lundgren, Kuklane et al. 2013[28])
	Reduction of radiant heat (Gao, Kuklane et al. 2018[29])
	Increasing air velocity (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019[27])
	Application of occupational health principles (Lundgren, Kuklane et al. 2013[28])
	Engineering and administrative controls (Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019[26])
	Personal cooling techniques (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018,[29] Nunfam, Van Etten et al. 2019[25])
Individual control	Adjust working schedule (Xiang, Hansen et al. 2016,[20] Nunfam, Oosthuizen et al. 2019,[26] Pogacar, Znidarsic et al. 2019[24])
	Drinking sufficient water (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Arjona, Pineiros et al. 2016,[30] Xiang, Hansen et al. 2016,[20] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
	Drinking lemon water, fructose, and sugarcane juice (Arjona, Pineiros et al. 2016[30])
	Wearing large hats or caps (Xiang, Hansen et al. 2016[20])
	Taking breaks in the shade (Xiang, Hansen et al. 2016,[20] Nunfam, Oosthuizen et al. 2019,[26] Pogacar, Znidarsic et al. 2019[24])
	Wear appropriate clothes (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Xiang, Hansen et al. 2016,[20] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
	Self-pacing (Lundgren, Kuklane et al. 2013,[28] Xiang, Bi et al. 2014[21])
	Acclimatization (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013,[23] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019,[26] Nunfam, Van Etten et al. 2019,[25] Pogacar, Znidarsic et al. 2019[24])
	Open windows or use of natural cooling systems (Lundgren, Kuklane et al. 2013[28])
	Placing a handkerchief over the face or covering the face with wet white clothes (Pradhan, Shrestha et al. 2013[23])
	Bathing in cold water (Lundgren, Kuklane et al. 2013,[28] Pradhan, Shrestha et al. 2013[23])
	Reduction in work intensity (Lundgren, Kuklane et al. 2013,[28] Gao, Kuklane et al. 2018,[29] Moda, Leal et al. 2019,[27] Nunfam, Oosthuizen et al. 2019[26])

Descriptive analysis

With our review identifying 13 relevant studies out of the 6,176 eligible for data extraction, 9 presented information on climate change, occupational heat stress risks, and adaptation strategies. Most studies on the topic have also emphasized the future impacts of climate change including its adverse effects on occupational and public health, how climate change and high temperature and humidity create physiological challenges, and risks of heat-related illnesses; how climate change will affect occupational heat stress risk, particularly in low- and middle-income tropical and subtropical regions, and how these often intertwined with social impacts. Based on the search time interval in this study (2000–2019), 9 (69.23%) studies were published between 2014 and 2019. Of the 13 papers analyzed, 9 papers (69.23%) directly considered the impacts of climate change on workers’ health in different countries (Ecuador, Ghana, Nigeria, Australia, Iran, Greece, Slovenia, Africa, and Nepal). Overall, the topic trends identified in the papers included the effect of climate change on heat stress, heat strain, and health risks. Of the data abstracted based on the keywords adopted, 13 studies were selected and grouped into major themes that included an outline of risk factors and preventive methods for the impact of climate change on occupational heat strain among women workers.

Thematic content analysis

The main health impacts of climate change include heat cramps, respiratory difficulties, heatstroke, increased heart rate, increased core body temperature, increased sweating, impairment of the mental and physical performance, fatigue, nausea or vomiting, hot-dry skin, heat strain, depression, and anxiety. This systematic review summarizes published to date evidence regarding the role of climate change, particularly in workplaces with high temperatures, and how this affects occupational heat strain among women workers. Despite differences in study design and analysis strategies, the evidence presented in this systematic review indicates an association between heat strain and climate change. Among the included studies, the impacts of climate change on occupational heat strain was the major commonality between physiological responses and heat strain, whereas their major differences were management and engineering. Individual control methods were around the interventions considered. Broad findings from the studies revealed that exposure to extreme heat due to climate change was associated with negative health impacts and occupational heat strain. In addition, the need for sentinel effects and leading indicators to aid surveillance of climate-related occupational heat strain have been highlighted in several of the studies. Different control methods studies were considered among the ones included.

As well as heat strain, the kinds of health impacts sustained during hot and humid climatic conditions included “heat exhaustion, “dehydration,” “headache,” “heat rash,” “discomfort,” “dizziness’, “fatigue,” ‘irritability,” “lethargy,” “heat stroke,” “morbidity,” “mortality,” and “death.”

Risk factors that may increase susceptibility to climate-related occupational hazards

Environmental risk factors

The systematic review showed that among risk factors that may increase susceptibility to climate-related occupational hazards, the most studied risk factor was climatic condition (air temperature, heatwave, extreme weather, etc.). In tropical and subtropical countries, atmospheric pressure, solar radiation, ultraviolet radiation, heat, relative humidity, air pollution, air movement, and waste generation should also be considered environmental risk factors. In three studies, workstation situations such as ergonomic risks (body posture, movement, confined space, etc.) have been considered environmental risk factors.

Individual risk factors

Individual risk factors can include demographic factors, physical fitness, physical health, mental health, and lifestyle that play a fundamental role in heat tolerance. This review shows that most individual risk factors were age, sex, and BMI. Other individual differences included the effects of body fat content, disabilities, aerobic capacity, degree of acclimatization, health status, physical intensity, metabolic rate, insufficient fluid replacement, PPE,[36] and fitness level.

When working in heat, people with the highest risk are those with obesity, frail elderly or young workers, and people with physical health problems such as cardiovascular, thyroid, chronic, and respiratory diseases, diabetes, skin, and liver problems, pregnancy, medical conditions, heart disease, lung disease, kidney disease, infection disease, dehydration or poor hydration, insufficient sweat rate, heat illness history or injury, reproductive hormones, menstrual phase, breast-feeding, and malnutrition.[28]

Additional factors affecting heat tolerance include caffeine, alcohol and nicotine intake, and drugs such as nephrotoxins and non-steroidal anti-inflammatory drugs (NSAIDs).[30] Genetic susceptibility, ethnic origin, education level, and cultural aspects,[28] including human behavior can influence heat tolerance.

Vulnerable subpopulations identified included pregnant woman workers, younger workers aged 15–24 years, outdoor workplaces with exposure to solar radiation, and indoor workplaces with poor or no air-conditioning and no electrical fans. Young and elderly workers are likely to be more sensitive to hot and humid climate conditions. Men and women have different physiological responses, reproductive hormones, and body characteristics. Therefore, women due to having menstrual cycles, breastfeeding, and having a large surface area to body mass ratio have lower heat tolerance. Males may tolerate extremely hot–dry conditions but women may enhance their tolerance for hot–humid environments.

Organizational risk factors

In agricultural and chemical industries and other workplaces, climate change is likely to increase human exposure to harmful physical and chemical agents. The magnitude of the increase will be highly dependent on the contaminant type, amount of harmful physical and chemical agents, and type of exposure. Risks from many pathogens, pesticides,[31] noise[10] particulate, and particle-associated contaminants could increase significantly. One study shows that ultraviolet (UV) radiation[31] may be aggravated by an increase in climate change, air pollution, etc. Job-related risk factors such as income, individual work habits,[20] work characteristics (task complexity, concentration, etc.), poor working conditions,[30] physical demands of jobs, working around heat sources, and outdoor work (solar radiation), may be also aggravated by climate change. Equipment risk factors such as clothing properties (protective clothing, color of clothing, and size of clothing) should also be considered.

Risk factors related to facilities include poor or no air-conditioning or fans, large distances from cool restrooms, poor access to safe drinking water or large distances from drinking water location,[10] and absence of trees and vegetation in urban areas.[27]

Risk factors related to management include work shift, time spent indoors/outdoors, duration of break/rest hours, inadequate prevention and control policies,[27] middle- and low-income countries, inadequate awareness of heat stress risks, lack of training and skills, years of occupational health and safety (OHS) work experience,[25] fewer drinking rest breaks,[10] and lack of occupational health and safety programs.[21]

Controlling factors of climate change and occupational heat strain

Individual control

Individual control can include drinking sufficient water, wearing appropriate clothes, acclimatization, self-pacing,[21,28] reducing work intensity, adjusting work schedules, taking shaded breaks, and wearing large hats or caps[20]. Workers’ self-pacing has been found to reduce occupational heat strain in some countries. Positive self-pacing can be considered as a physiological strain and psychological response to heat stress, and heat strain reduction by adjustment of work rate. This factor may be an important protective behavior and response for many workers in severe thermal conditions.

Engineering control

Work/rest cycles with a heavy workload and severe intensity in hot–humid environments should be intermittent, and continuing work in this situation should be strictly forbidden. Rest times to cool and rehydration should be included in meals by drinking water or electrolyte drinks containing salt and body washing or taking a shower. Engineering control can include designing proper cooling, air conditioning, and electric fans, heat-shield projects, insulating workplace buildings,[28,31] using early warning and emergency response systems, eliminating or reducing heat sources, increasing air velocity, and applying occupational health principles[28]. Engineering controls including insulation of cooling systems, air conditioning, electric fans, and insulation of workplace buildings to reduce heat exposure from outside should be available to employers at all workplaces with hot processes. Yet, substantial numbers of workers are experiencing the health effects of elevated temperatures, in combination with climate change extremes and the effects of air pollution, which have potential impacts on their heat strain and well-being caused by air pollution emission control.[27] In addition to the various preventive approaches to heat strain, it is important to note that suggestions for mitigation of ongoing global climate change such as reducing greenhouse gas emissions,[28] using renewable energy for cooling systems, identifying the locations in the world with hot seasons, development guidelines, risk assessment and standards, and identifying new climate models are key methods to protect future generations of workers from any growing climate-related occupational heat strain.

Managerial control

Management control can include proper continuous education and training, the use and improvement of guidelines, risk assessments, indices and standards, adjustment of work/rest cycles, adequate supply of clean drinking water and electrolyte drinks near the workstations or in short distances, selection criteria when recruiting workers, rearrangement of work tasks to cooler parts of the day and season, proper appropriate personal protective equipment (PPE), proper cold rest places, use of global ‘Hothaps’ program, identification of new climate models,[29] keeping trees or other things that create shade (roof or walls), medical monitoring, compensation, social protection and payment per hour,[26] and enabling self-paced working through the empowerment of employees.

In this study, if we want to categorize the effective factors that can induce occupational heat strain, environmental factors are around 65–70%, occupational factors around 20–25%, and individual factors around 5–10%. In contrast, the weight of environmental factors is much higher than occupational factors and individual factors. However, the number of individual factors is higher than the environmental factors. By examining the thermal indexes, it can be seen that environmental factors have been expressed as the main factor and only a small number of indicators have included individual factors. The coefficients of environmental factors were more than individual factors. In total, personal characteristics in addition to main agents, including the environmental factors, play an important role in producing thermal strain.

Outdoor workers are particularly vulnerable to heat exposure and more likely to suffer from heat stress, indoor workers around heat sources with non-air-conditioned work environments are also at risk of heat strain and injury despite the reduced exposure to sunlight radiation. In total, organizational factors in addition to main agents and sub-domain job-related categories play an important role in producing thermal strain. Of the job items, sub-domain jobs related to working around heat sources and physical demands of jobs had a similar effect on heat strain because increased heat sources can enhance the physiological and perceptual strain and then perceived physical demands. Of organizational items, the greatest indirect effect belonged to the management of the heat stress risk factors. It is clear that thermal stress control influences directly the ambient temperature of the workplace and indirectly the physiological factors such as core body temperature, skin temperature, and heart rate. Other domain-organizational, sub-domain-facilities, and equipment (clothing items, thickness) play an important role when other control measures are not completely implemented. The present systematic review Quantitative Risk Assessment (QRA) model to evaluate the risk of thermal stress and strain was not done.

DISCUSSION

With the influence of global warming resulting in higher temperatures and more hot days, we might expect to see a rise in occupational heat strain and heat-related illnesses. The impact of heat-related illnesses may be reduced by adapting vulnerable groups such as pregnant women, younger women workers aged 15–24 years, and old workers to temperature increases.[40] Jianjun et al. showed that young and old workers have less heat-related training compared to middle-aged workers, and young workers have less satisfaction and are eager when it comes to preventing heat stress. They tend to hold negative attitudes toward their employers and occupational health recommendations and are less concerned about heat exposure than old ones. Therefore, further heat education and training should focus on those undertaking physically demanding and manual work in both outdoor and indoor occupations, particularly in these two age groups.[20] Another point is to consider that reproductive hormones (estrogen and progesterone levels) may influence the thermoregulatory system. These hormones are reported to alter baseline core body temperatures, sweat rate, blood pressure, skin blood flow, and metabolic rate. The impaired capacity to dissipate heat leads to greater heat storage in older females, which is more pronounced with increases in the level of heat stress.[41,42]

The difference in regulating temperature is usually evidenced by the greater body temperature, which is quite harmful to women in very hot environments. Compared with men, women require (a) a considerable amount of fat that acts as an insulator and increases heat or thermal storage; (b) a thermoregulation system for high temperatures; and (c) less aerobic capacity, which increases the relative working load of activity. Researchers have found that men have less heart rates than women for a given level of heat stress. Also, the area of the body covered is greater in women than men in Islamic communities, which probably affects the heat transfer between the body and the environment.

Mehnert et al. showed that sweat loss to adjust anthropometric variables and physical fitness in women differs from that in men. Accordingly, excessive sweating in women can lead to loss of body heat storage and core body temperature.[43] Also, based on the study conducted by Ashley et al., a higher core body temperature in females under critical conditions, that is, high temperature and workload, compared to men can lead to a possible approach to revising the threshold limit value for maximum sweat rate and core body temperature in women (Ashley et al. 2008).[44]

Pregnant women who have weak immune systems when exposed to extreme heat are faced with additional health risks, including poor pregnancy health, malformations of the fetus, and negative birth outcomes. Therefore, physical intensity guidelines and work/rest cycles should be set by physicians as scientists are continuously re-evaluating the safest limits according to the available standards and scientific advice.[31,44] Changes in thermoregulation and blood pressure during pregnancy vary in exposure to heat due to hormonal influences, sympathetic nerve activity, vascular stiffness, and other variables on neural control of skin blood flow and sweating.[42] The result of this systematic review shows that pregnancy status in women workers in exposure to heat and humid climate conditions can be dangerous for expecting mothers.

Women differ from men in physiology, perceptual responses, and thermoregulatory systems due to sex hormones (estrogen and progesterone levels) released during menstrual cycles. In the same experimental studies which eliminate some differences among the two groups, women’s sweating response to heat stress is still smaller than that of men, but they are able to maintain their core body temperature with a greater sweating rate. The threshold for the onset of sweating is found at a higher level of core temperature for women; under identical exposure climate conditions, women tend to have higher core temperatures, and physiological and perceptual responses to positive or negative hot–humid climate conditions, depending on the phase of their menstrual cycle.[10,43,45]

Comfort perceptions vary with BMI and ethnicity, people with a low BMI (BMI <18.5 kg/m²) are comfortable at hot temperatures, whereas people with a high BMI (BMI >25 kg/m²) expressed comfort at low-to-moderate temperatures under different climate conditions.[46] Adams et al. showed the effects of obesity and non-obesity on body temperature in healthy females when controlling hydration and metabolic heat production during exercise in warm environments (40°C, 30% humidity) for 60 min; there were no differences in body temperature between the two groups, that is, obese and none-obese.[47]

Protective clothing can create a serious heat strain as it can have properties that inhibit sweat rate, increase core body temperature, skin temperature, and cause excessive sweating. Determining human body heat balance is an important factor and can be indirectly reflected in heat stress prevention plans and control measures. Employees in chemical laboratories and industries need to wear protective clothing to protect themselves from toxic vapor and chemical hazards that induce increased metabolic rates, reduce heat tolerance, decrease air movement over the skin, and cause discomfort. Thus, it is important that the basic aspects of clothing properties are appropriately managed in all workplaces that are exposed to hot and humid climate conditions.[15,20,23,24,25,26,27,28,29] ACGIH provided the wet-bulb globe temperature (WBGT) adjustment values for several standard clothing ensembles that should be considered when people wear different protective clothing, and the grade of clothing adjustment factor is to be added to the reading of the ambient environment and then compared to an occupational exposure limit.[48,49] Traditional Islamic laws and customs prohibit Muslim women from wearing revealing and short clothes in hot workplaces or when exercising. Compared to other countries, for example, European ones, in Islamic countries, women workers should wear hijab, covering everything except the face and hands up to the wrists; such a dressing style can affect their physiological and perceptual responses, especially in hot seasons (Chan et al. 2016).[50] This type of Muslim clothing potentially imposes greater heat strain on Muslim women during work due to reduced heat loss and air movement from the skin and presents critical thermoregulatory problems, especially in hot environments. Although the impact of heat stress and occupational heat strain on health is well established, the effects of risk factors (clothing, inadequate sanitation facilities, etc.) and climate change on Muslim women workers remain unexplored. Policymakers and employers should consider urgent gender-sensitive policy interventions to protect the future health and physiological performance of Muslim women workers due to clothing restrictions.[17,32,50]

This systematic review indicates that heat stress, heat strain, and climate change training are the workers’ major sources of information about heat stress prevention worldwide, and this is the case for occupational health in general. Women workers should have a good knowledge of symptoms of excessive heat exposure and the impacts of climate change on heat strain, especially young workers and those over the age of 55 years. Mass media also plays an important role in improving heat strain prevention information and organizing public opinion.[20]

To reduce the impacts of climate change on occupational heat strain, the potential risk of heat strain needs to be recognized and then effective adaptation devices such as using appropriate personal cooling devices, PPE, acclimatization, and self-pacing should be provided.[23] It has been suggested that adaptation to climate change for vulnerable people can be improved by social networks available to individuals, and employers should consider how these networks shape perceptions explicitly.[51]

Moyce et al. showed that sweat loss to adjust anthropometric variables and physical in women differs from that female worker paid by the amount of produce harvested among agricultural workers (versus by the hour) have greatly increased the developing acute kidney injury. Women may tend to limit drinking or eating during their work shift to reduce their need to use the facilities or may delay trips to the bathroom during the workday out of fear for their safety compared to men workers (Moyce et al., 2017).[52] Therefore, when the worker is exposed to heat sources in hot seasons or other times, adequate and sufficient drinking water at work must be available, and the possibility of drinking enough water while at work should be taken into account. In cases where this is not possible, a doctor may recommend the use of salt to help increase electrolyte balance.

In women, there are conflicting descriptions of the plasma volume response to exercise and heat stress even when the phase of the menstrual cycle has been controlled. A hemoconcentration during both the pre-ovulatory and post-ovulatory phases of the menstrual cycle was observed in a study conducted in hot environmental conditions. Also, the hypothesis that women hemoconcentrate less during passive heating in the follicular than in the luteal phase is new, and the explanation for such a phenomenon is incomplete (de Jonge et al. 2003).[53]

Based on some studies, the systematic strategies to protect women workers such as traffic police, agricultural and construction workers from heat exposures include providing an umbrella to each work station and a large hat or cap for shade, providing cooling vests, lightweight shoes, and quality goggles for each staff member, work organization that promotes worker self-pacing, rotation of personnel standing directly in the heat, providing cool potable water, and personal water bottles, toilet facilities, oral rehydration satiations, anti-heat stress clothing, and portable fans.[15] The role of training in tolerating and eliminating heat stress exposure and physiological responses in some studies under different climate conditions has been discussed. Tomoko et al. found that short-term physical training improves physiological responses during moderate exercise in a hot environment by decreasing the core body temperature and enhancing the sweating rate, which might be affected by the phase of the menstrual cycle, and in young women, the effects of training are apparent within the first month of training.[52]

Medical monitoring by a licensed physician in selection criteria when recruiting workers should be done before heat exposure to ensure workers are not exposed to heat stress exceeding NIOSH’s RAL for both acclimatized and unacclimated workers (2018). In a study conducted by Rivera-Brown et al., the result showed that exercise and heat-acclimatization among girls and women exhibit similar cardiovascular and thermoregulatory adjustment while exercising in a hot and humid outdoor environment (33.4°C and 55.1% RH). The fact that acclimation to heat among women workers reduces physiological responses under different hot–humid climate conditions of workplaces is of great importance.[53]

To minimize occupational heat strain in warm or hot environmental conditions, it is recommended that women workers, occupational health professionals, and employers regularly review the potential impacts of heat stress on workers’ health and performance. Therefore, women workers, occupational health professionals, and employers can adopt the most effective heat stress and strain prevention strategy and have safe work practices/safe job procedures.[54]

Limitations

There was a limited number of included studies that focused specifically on women workers. The included studies constituted only a small portion of the entire population of working women worldwide, especially in tropical, subtropical, and Islamic countries. Caution should be taken when generalizing the results to female workers. Finally, the effects of climate change on other occupational factors such as productivity loss, accidents, loss of working hours, and mental health problems have not been assessed.[55] Given that no records of specific actions were available for women worker populations, the impact of climate change on occupational heat stress and strain can only be estimated based on the limited set of scenarios that these papers present. Further, it cannot be assumed that these results are generalizable to all women workers all over the world because of the legal and social environment under which labor unions run.

CONCLUSION

In summary, climate change is a fundamental aspect of occupational heat strain, particularly in tropical and subtropical regions with low and middle incomes. Available data in this systematic review article suggest that there is a high incidence of heat strain among the women working population. The current systematic review provided some suggestions and recommendations for women employers, stakeholders, occupational health professionals, and health care providers for developing policies and strategies for mitigating occupational heat strain due to climate change and could help suggest control solutions and preventive measures that can be significant not only for current but also for future women working. The threshold limit value can be reconsidered for preventing heat strain, cardiac stress, and maximum sweat rate for women workers and their health parameters.

The following research areas are proposed in the assessment of climate change impacts on occupational heat strain among women:

• (1) Assessing the effects of climate change among vulnerable outdoor and indoor women workers, such as pregnant, young, and elderly workers

• (2) Association between occupational heat strain from critical climate change and the effects of gender, clothing, migration, and metabolic rate

• (3) The development of mitigation and adaptation strategies for global change in the future

• (4) The development of guidelines, programs, and standards that are fast, practical, inexpensive, and simple for primary measures to reduce the impacts of climate change on occupational heat strain among women workers now and in the future

• (5) The development and continuous training of management, engineering, and individual solutions for eliminating heat strain risk factors related to climate change.

Funding

This research has been supported by the Tabriz University of Medical Sciences & Health Services [grant number 65323; the ethical code: IR.TBZMED.REC.1399.548]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.