Impact of Air Conditioners on Sick Building Syndrome, Sickness Absenteeism, and Lung Functions

Abstract

Introduction:

Modernization has led to greater usage of Air Conditioners (ACs) in our daily lives. It is observed that the occupants of office buildings with ACs consistently report on average more symptoms than do occupants of office buildings with natural ventilation referred to as Sick Building Syndrome (SBS). The appearance of symptoms reduces work efficiency and increases absenteeism due to sickness (sickness absenteeism). Therefore, the present study was planned to evaluate the impact of usage of ACs on SBS and to find out the association of ACs with sickness absenteeism and lung function tests.

Materials and Methods:

This study was conducted on 200 healthy non-smoker adults in the age group of 18 to 45 years who were using ACs for at least 6 to 8 h/day for more than 2 years (group I). And 200 healthy adults, age and gender-matched, with the same work pattern, not using ACs at all served as controls (group II). The basic information on the usage of ACs and the prevalence of discomfort related to neural symptoms, respiratory symptoms, and skin and mucous membrane related to SBS was obtained through a questionnaire.

Results:

The building-related symptoms in group I males were more compared to group II males and significantly higher in group I males compared to females. We observed that the appearance of symptoms of SBS led to sickness absenteeism among group I participants. Lung function tests especially FVC, FEV1, PEFR, and MVV were significantly reduced among group I males and females compared to group II males and females.

Conclusion:

ACs have a profound effect on the quality of the air we breathe and on human health than just lowering the temperature. There is a higher prevalence of SBS-Respiratory and allergic symptoms in AC users.

INTRODUCTION

In the present modern days, the usage of Air Conditioners (ACs) has become an essential element in our daily lives. The ACs are being used extensively to improve the standard of living in workplaces, living places, as well as while traveling. Despite the advantages of using ACs, there are reports of a few undesirable effects of ACs on human health.[1,2] Cold dry air from ACs increases the risk of atopic sensitization[3] and trigger epithelial cell response leading to an increase in nasal secretion.[4,5] There are reports of increased prevalence of IgG-induced sensitization and hypersensitivity pneumonitis in persons exposed to aerosols of contaminated ACs.[6] Recent evidence suggests that aerosol spread of transmission of the virus is possible in an indoor environment with HVAC systems.[7]

It is observed that occupants of buildings with ACs consistently report on average more symptoms than occupants of buildings with natural ventilation, despite the quality of air being better in air-conditioned buildings. The symptoms include ophthalmic symptoms (dry, itchy, strained, and tired eyes), allergic symptoms (stuffy nose, mucous membrane irritation, runny or stuffy nose, breathing difficulties, and dry throat), and general and neurological symptoms (headache, lethargy, and fatigue). This set of non-specific symptoms occurring in those who live or work in modern air-conditioned buildings are referred to as Sick Building Syndrome (SBS).[8] All these symptoms occur in the general population and people working in naturally ventilated buildings also, but they are more prevalent in air-conditioned buildings. An explanation for the increased prevalence of SBS in air-conditioned buildings could be that the ventilation systems in buildings with ACs disseminate contaminants into the indoor air. What these contaminants are and through which biological response mechanisms they cause a pattern of non-specific symptoms is not clear.[5] Another evidence suggests that inadequate ventilation, presence of visible moisture, and molds in buildings with ACs are consistently associated with increased risk of respiratory symptoms, asthma, and musculoskeletal symptoms.[9,10,11]

The appearance of symptoms reduces work efficiency and increases absenteeism due to sickness (sickness absenteeism).[12] The symptoms usually disappear hours or in some cases days after removal from that environment.

In air-conditioned rooms, the temperature, humidity, and air velocity are maintained constant. Hence, staying in an air-conditioned environment for a long time can lead to thermal regulation stress due to disturbance in the thermal adaptation and reduced tolerance to a hot environment because of frequent switching between indoor and outdoor temperatures.

Hence, there is a need to define the consequences of repeated exposure to ACs on human health. Therefore, the present study was planned to evaluate the impact of usage of ACs on SBS and to find an association between air conditioning, sickness absenteeism, and lung functions tests.

AIMS AND OBJECTIVES

1. To evaluate the impact of usage of ACs on SBS and sickness absenteeism.

2. To assess the lung functions in AC users.

MATERIALS AND METHODS

This study was conducted from May 2019 to June 2020 on 400 healthy non-smoker adults in the age group of 18 to 45 years after obtaining the Institutional ethical committee clearance. A total of 200 adult employees were selected randomly working in two software companies, one restaurant, and one mall in Hyderabad city who used ACs for at least 6 to 8 h/day for more than 2 years with indoor temperature maintained between 18°C and 22°C (group I) served as subjects. And 200 healthy adults, age and gender-matched, with the same work patterns who were not using ACs at all and staying in naturally ventilated buildings served as controls (group II).

Exclusion criteria

1. Presence of any acute/chronic respiratory disorders or other chronic illness

2. Systemic illness which directly or indirectly affects the respiratory system

3. Smokers

4. Use of ACs irregularly

After taking consent, a detailed personal history, information on the usage of ACs, anthropometric parameters, and prevalence of discomfort related to neural symptoms, respiratory symptoms, and skin and mucous membrane related to SBS were obtained from subjects and controls through a simple self-completion questionnaire. The responses were obtained on a 5-point scale, reflecting the frequency of the symptoms (1 = never, 5 = always). Quantification of perceptions and the responses were converted into SBS scores. The respondents were defined as having SBS, if they have an SBS score of 1 or above and if symptoms resolved while away from workplace. The data on Sickness absenteeism of all the participants who have taken sick leave or absent from work on grounds of sickness (except Women on maternity leave) and leave without pay was collected for the previous year from the data obtained from attendance registers. The quantified answers from the questionnaire were then subjected to statistical analysis to evaluate the relationship between SBS and AC usage.

The lung functions were assessed using a computerized spirometer HELIOS 702 after giving thorough instructions. The tests were performed in a sitting position and the best among three consecutive readings was selected. The results were interpreted in accordance with the latest guidelines for pulmonary function tests (PFT) by the American Thoracic Society.[13] The outcome was presented as mean ± SD for each parameter. The degree of significance was calculated using the unpaired student t-test for different groups while comparing and P value <0.05 was considered significant.

The data were analyzed using the statistical software SPSS-23.

RESULTS

A total of 392 adults (196 subjects and 196 controls) participated in the study with a 98% response rate. More than half of the subjects (57%) were males (112) in group I. The same number of males (n = 112) and females (n = 84) were selected as controls in group II. The mean age of participants was 28.2 (SD ± 6.8).

In the present study, the symptoms of SBS are more prevalent in group I males compared to group II males and significantly greater in group I females than males. The most common symptoms prevalent were ophthalmic symptoms in subjects which included strained, tired eyes (48%) and dry itching eyes (46%) [Table 1]. The second most common symptoms prevalent were the respiratory symptoms which included dry sore throat in 43% of subjects, followed by a runny nose (40%), sneezing (38%), stuffy nose, and sinus congestion (37%). The general symptoms that were most prevalent were headache (27%) followed by lethargy (23%). Difficulty in breathing was the least prevalent symptom. We observed that most of the symptoms started occurring during morning hours between 9 am and 11 am and worsened between 2 pm and 4 pm. The participants spent most of the time in the same place of their workplace and symptoms followed the same time pattern. Two of the subjects without previous history of asthma developed a wheeze.

Table 1.

Prevalence of sick building related symptoms in Group I and Group II

Symptoms	Prevalence (%) in AC users (Group I)				Prevalence (%) in non-AC users (Group II)
	Males n=112		Females n=84		Males n=112		Females n=84
	n	%	n	%	n	%	n	%
Ophthalmic symptoms
Dry, Itchy eyes	46	37	46	53	11	10	14	16
Strained, tired eyes	48	42	62	72	17	15	19	22
Respiratory symptoms
Dry and sore throat	43	38	56	65	8	7	10	12
Stuffy nose, sinus congestion	37	32	41	48	14	12	15	17
Sneezing	38	33	34	40	5	4	11	13
Runny nose	40	35	41	48	8	7	8	9
Cough	18	16	23	27	8	7	8	9
Difficulty in breathing/shortness of breath	1	0.8	0	0	0	0	0	0
Wheeze	2	0.2	3	3	1	1	0	0
General symptoms
Fatigue, dizziness, malaise	15	13	22	26	5	4	5	6
Dry, itchy, irritated skin	10	9	12	14	4	3	4	5
Dizziness, light headedness	12	10	16	19	2	1	3	3
Headache	27	24	30	35	5	4	8	9
Lethargy	23	20	32	37	6	5	13	15

The data revealed that the sickness absenteeism among male subjects was 22 ± 2 days/year and 31 ± 3 days/year in female subjects (group I) compared to 13 ± 6 days/year in male controls and 15 ± 4 days/year in female controls (group II) [Table 2]. This shows that sickness absenteeism is more among AC users (group I) than non-AC users (group II) and significantly more in females compared to males.

Table 2.

Sickness absenteeism in Group I and Group II

Ac users (Group I)				Non-AC users (Group II)
Males (n=112)		Females (n=84)		Males (n=112)		Females (n=84)
Total No of working days/year	Days absent due to sickness/year	No of working days/year	Days absent due to sickness/year	No of working days/year	Days absent due to sickness/year	No of working days/year	Days absent due to sickness/year
234	22±2	234	31±3	234	13±6	234	15±4

Lung functions are known to be associated with anthropometric measures. However, there were no significant differences in anthropometric features of males and females between the two groups. The lung functions were compared among male subjects with male controls [Table 3] and female subjects with female controls [Table 4]. There was significant reduction in mean values for FVC (2.93 ± 0.46) in male subjects (group I) compared to male controls (3.49 ± 0.46) (group II) (p < 0.001). Similarly, there was a significant reduction in the mean value for FVC in female subjects (group I) (2.3 ± 0.51) compared to female controls (2.51 ± 0.28).

Table 3.

Comparison of anthropometric parameters and lung function tests in Group I and Group II Males

Lung function tests/parameter	AC Users (Group I) Males (n=112)		Non-AC Users (Group II) Males (n=112)
	Mean	SD	Mean	SD	SE	P
Age	30.38	5.8	30.98	5.91	1.036	>0.05
Height	168.56	7.05	169.7	6.7	1.2	>0.05
Weight	68.7	8.7	69.61	7.7	1.44	>0.05
FVC	2.93	0.46	3.49	0.46	0.08	<0.001
FEV1	2.49	0.46	2.71	0.41	0.08	<0.01
PEFR	7.1	0.74	8.18	0.96	0.15	<0.001
FEF 25-75	4.25	0.72	4.29	6.7	0.122	>0.05
FEV1/FVC	90.8	4.2	89.7	5.57	0.9	>0.05
MVV	108.52	12.04	120	13.75	2.3	<0.001

P<0.05 is significant

Table 4.

Comparison of anthropometric parameters and lung function tests in Group I and Group II females

Lung function test/Parameter	AC Users females (n=84)		Non-AC Users females (n=84)
	Mean	SD	Mean	SD	SE	P
Age	27.4	2.96	28.6	5.4	1.036	>0.05
Height	156.8	5.83	157.5	4.5	1.2	>0.05
Weight	57.74	6.11	55.45	5.06	1.44	>0.05
FVC	2.3	0.51	2.51	0.28	0.098	<0.05
FEV1	1.99	0.49	2.66	0.29	0.09	<0.01
PEFR	5.2	0.69	6.02	0.65	0.16	<0.001
FEF25-75	3.49	0.39	3.57	0.24	0.07	>0.05
FEV1/FVC	88.5	6.89	88.5	6.96	1.65	>0.05
MVV	89.2	9.88	97.9	7.06	2.06	<0.01

P<0.05 is significant

There was also significant reduction in mean value for FEV1 in group I males (2.49 ± 0.46) and group I females (1.99 ± 0.49) compared to group II males (2.71 ± 0.41) and females (2.66 ± 0.09) (p-value < 0.01). The mean value for PEFR in group I males (7.1 ± 0.74) and group I females (5.2 ± 0.69) was significantly less than group II males (8.18 ± 0.96) (p-value <0.001) and females (6.02 ± 0.65) (p-value <0.001). The mean value for MVV in group I males (108.52 ± 12.04) and females (89.2 ± 9.88) were less compared to group II males (120 ± 13.75) and females (97.9 ± 7.06) (p-value <0.01). Thus, FVC, FEV1, PEFR, and MVV were significantly reduced among male and female AC user's compared to male and female non-AC users. There were no significant differences in the mean values for FEV1/FVC and FEF-25-75 between the two groups.

DISCUSSION

The naturally ventilated buildings often have conditions of temperature and ventilation outside the recommended standards. However, in the present study, participants working in naturally ventilated buildings had fewer symptoms of SBS and less sickness absenteeism than those working in air-conditioned buildings. Earlier studies have also reported[14] a significant increase in sickness absenteeism 6 days/100 workers/month in a group moving from naturally ventilated to an air-conditioned office and there was clearly a linear relationship between the number of work-related symptoms and self-assessed productivity. Similarly, Sahakian et al.[15] reported an association between dampness and air-conditioning in homes and offices and increased prevalence of sick leave attributed to respiratory symptoms and medical visits similar to the results in our study.

The absence of workers from office buildings with ACs at a considerable level is due to the symptoms of SBS. Our study showed that the frequency of symptoms was higher in subjects using ACs than in controls. The most common symptoms prevalent in workers in air-conditioned buildings were ophthalmic symptoms, followed by respiratory symptoms and general symptoms. The factors like low fresh air ventilation, poor control of temperature, lighting, and accumulation of possible contaminants within the indoor environment of air-conditioned buildings could result in a higher prevalence of occupant-related symptoms leading to various health problems.[16,17] The higher prevalence of respiratory symptoms in our study is in line with the results of other studies.[18,19] Cold dry air from the ACs causes activation of the epithelium to generate pro-inflammatory substances and engorgement of venous sinuses in the submucosa which leads to congestion, sneezing, and rhinorrhea. Repeated cooling and desiccation of peripheral airways can cause airway remodeling similar to that seen in asthma. There is a potential for transmission of toxic volatile substances via an air conditioning system. In a study done by Gerber et al.,[19,20] low dose exposure to volatile chemicals by the air conditioning system induced an acute asthma attack and suggested that air conditioning can lead to incidents of inhalation occupational exposure/intoxication to other employees in the same building.

In the present study, two of the subjects using ACs with no previous history of asthma, developed a wheeze. Repeated exposure to cold air can increase the granulocytes and macrophages in the lower airways.[20]

In this study, four parameters of lung functions, that is, FEV1, FVC, PEFR, and MVV were found to be significantly reduced in male and female subjects using ACs for a prolonged time. These results are in congruence with studies by S. Nasreen et al.[21] and Sandip M Hulke,[22] who reported that there was a significant reduction in FEV1, FEF25-75, and PEFR values and also a reduction in chest expansion in subjects exposed to ACs.

A significantly reduced FVC and FEV1 values and normal FEV1/FVC suggest a restrictive type of respiratory disorder. The respiratory tract of the subjects using ACs becomes hyperresponsive and there is desquamation of airway mucosal epithelium, inflammation, and bronchoconstriction due to breathing in dry cold air.[23] There is a loss of epithelial relaxing factor leading to decreased patency of airways resulting in reduced FEV1 and PEFR values. A significant reduction in PEFR indicates blockage of airways.

CONCLUSION

ACs and indoor air have a profound effect on the quality of the air we breathe and on our health than just lowering the temperature. There are higher prevalence of SBS-respiratory and allergic symptoms in AC users than in people working in naturally ventilated buildings leading to absenteeism from work. Hence, approaches to identify SBS in the working environment are very important and there is a need to study the protective measures to cut back the undue risk of ACs. Regular cleaning of ACs to ensure good indoor air quality and spirometry screening to detect early changes can improve the health and well-being of AC users and reduce the economic burden of lost work time and costs spent on health and medicines. The AC manufacturers must respond by providing newer methods of improving indoor air and developing air-cleaning products.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.