Rubber latex processing acid poisoning in India: Epidemiology, clinical outcomes, and forensic insights – A systematic review

ABSTRACT

Background:

Formic acid poisoning is a significant toxicological emergency in India, particularly in rubber-producing states. Despite its corrosive and toxic nature, its unrestricted access contributes to frequent cases of self-harm and accidental exposure. This review synthesizes available evidence on epidemiology, clinical manifestations, management strategies, patient outcomes and forensic insights in details.

Methods:

A systematic review of selected studies focusing on formic acid poisoning in India was conducted. The review followed PRISMA guidelines to ensure a structured and comprehensive approach. Studies were identified through searches in PubMed, Google Scholar, Scopus and web of science. Data extraction focused on key variables, including patient demographics, mode of poisoning (intentional vs. accidental), clinical presentation, treatment interventions, and outcomes in the form of recovery or death.

Results:

This systematic review analyzed 10 studies on rubber latex processing acid poisoning in India, highlighting epidemiology, mortality, morbidity, clinical findings, management, and autopsy findings. Poisoning was prevalent in rubber-growing regions, mainly affecting workers. Mortality ranged from 35.4% to 97.6%, with severe acidosis and organ failure as key contributors. Early dialysis improved survival, while delayed treatment led to fatal complications.

Conclusion:

Formic acid poisoning remains a severe public health issue. Effective regulations, improved awareness, and early medical intervention, including airway management and dialysis, are essential for better survival outcomes. Policy changes are necessary to limit accessibility and enhance awareness among high-risk populations.

Background

Formic acid is an organic corrosive agent widely used in rubber processing, textile, and chemical industries due to its strong coagulating properties. Its easy availability has made it a common agent in both accidental and intentional poisoning cases. Despite being a corrosive substance, formic acid remains largely unregulated in many parts of India, leading to its misuse.

According to the National Crime Records Bureau data published in 2022, poisoning accounts for a significant percentage of suicides in India. In 2022, poisoning was responsible for 28.1% of total suicides, with chemical agents like acids being among the leading causes.[1] Among agricultural labourers, accidental ingestion of toxic chemicals, including formic acid, remains a critical concern. The widespread use of formic acid in rubber plantations and its easy accessibility further exacerbate the issue. The problem is particularly acute in rubber-producing states such as Kerala, Tripura, Karnataka and Telengana, where occupational exposure is high.[2,3,4,5,6,7,8,9,10,11,12]

The pathophysiology of formic acid poisoning involves rapid absorption from the gastrointestinal tract, leading to systemic acidosis, mitochondrial dysfunction, and multiorgan failure. The corrosive properties result in significant damage to the oesophagus and stomach, manifesting as haemorrhage, perforation, and subsequent infection. Complications such as acute renal failure, severe metabolic acidosis, and circulatory collapse contribute to the high fatality rates associated with poisoning if not managed promptly.[3] The high fatality rate associated with its ingestion underscores the need for improved clinical protocols and regulatory policies.

Primary care physicians (PCPs) are often the first point of contact for workers exposed to these hazardous substances. Their role in early diagnosis, management, and referral is essential in preventing severe health outcomes and long-term complications associated with acid poisoning.

Despite its severity, there is limited awareness and regulation concerning formic acid poisoning. Unlike organophosphate poisoning, which has established treatment guidelines, the management of formic acid toxicity remains inconsistent across hospitals. Early intervention, particularly airway protection and dialysis, significantly improves patient survival.[9] However, a lack of standardized treatment protocols contributes to delayed and inadequate medical response in many cases.

This review aims to analyze the epidemiology, clinical manifestations, management strategies, patient outcomes and autopsy findings associated with formic acid poisoning in India. By synthesizing existing literature and identifying gaps, this study provides insights into potential preventive measures and policy recommendations to address the growing burden of formic acid toxicity.

Methodology

The systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered in PROSPERO under reference no. CRD420251002470,[13] as shown in Figure 1.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses model for study selection

Screening of articles and search strategy

A systematic literature search was conducted using PubMed, Scopus, Web of Science, and Google Scholar database and registers. Boolean operators were used to refine the search strategy, combining terms for specificity and sensitivity. The search string included: (“formic acid poisoning” OR “rubber latex processing acid poisoning”) AND (“fatalities” OR “deaths” OR “mortality”) AND (“management” OR “treatment” OR “clinical outcomes”). References from relevant studies were also screened for additional sources. Searches were restricted to articles published in English. Duplicate studies were removed, and two independent reviewers screened the titles and abstracts of identified articles. Full-text articles were searched for potentially eligible studies. The criteria for inclusion were (1) studies published in English between 2000 and 2024; (2) studies that provided primary data on epidemiological trends, clinical manifestations, treatment strategies, and patient outcomes in the form of morbidity and mortality; (3) observational studies (cross-sectional, cohort, case series, case reports; and (4) studies involving human subjects exposed to formic acid poisoning. The criteria for exclusion were (1) letter to editors, short communications, and grey literatures like conference abstracts, (2) studies that did not provide clear clinical or epidemiological data, (3) articles focusing solely on animal studies or industrial exposure without clinical manifestations, and (4) studies lacking sufficient methodological detail or data for extraction.

Data extraction and quality assessment

Data were extracted using a structured format covering demographics, mode of poisoning, clinical presentation, treatment interventions, and patient outcomes. Demographic variables included age, sex, and region, while poisoning was classified as intentional or accidental. Clinical manifestations encompassed gastrointestinal, respiratory, renal, and metabolic effects. Treatment approaches included supportive care, dialysis, endoscopic management, and antidotal therapy. Patient outcomes were assessed in terms of survival, complications, and mortality rates. Additional parameters such as occupational exposure, ICU admission, mechanical ventilation, long-term sequelae and death were noted. The Newcastle-Ottawa Scale was used to assess the quality of included studies as shown in Figure 2. High-quality studies were prioritized for synthesis of our review work.

Figure 2.

The graphical representation of the NOS assessment for Rubber latex processing acid poisoning studies. The bar chart represents the Selection, Comparability, and Outcome scores for each study and the red line plot shows the total NOS Score (out of 9) for comparison across studies. NOS = Newcastle-Ottawa Scale

Results and Discussion

This systematic review included 10 studies examining rubber latex processing acid poisoning in India, with a focus on epidemiology, mortality, morbidity, key findings, autopsy results, management strategies, and clinical outcomes. The included studies ranged from retrospective cohort studies, prospective observational studies, case series, and case reports. The sample sizes varied from single-patient case reports to large cohorts of 302 cases, reflecting the diverse settings in which formic acid poisoning has been studied.

This systematic review summary as depicted in Table 1, brings to light the confluence of an industrial practice (use of coagulating acids in natural rubber processing) with public health and safety issues in India. The findings show that formic acid, an essential chemical for small-scale rubber producers, has inadvertently become a common agent of poisoning in rubber-growing regions. The dichotomy is stark: On one hand, formic acid is valued for improving the efficiency of rubber sheet production; on the other hand, its ubiquity in rural homes has led to severe and often fatal toxic exposures.

Table 1.

A summary of the papers reviewed systematically

Authors	Type of study	Location	Sample size	Epidemiology	Mortality and morbidity	Key findings	Autopsy findings	Management strategies	Clinical outcomes
Dalus et al. (2013)	Retrospective study	Trivandrum, Kerala	302 cases	Males (60%); peak age 25–45 years	35.4% mortality; bowel perforation, ARDS had 100% fatality	Predictors of mortality include metabolic acidosis, oesophageal perforation, and respiratory distress	Esophageal perforation, lung injury	Endoscopic monitoring, esophageal dilation therapy.	50% develop esophageal strictures
Raghavan et al. (2018)	Prospective follow-up study	Alappuzha, Kerala	129 cases	High occupational exposure; long-term complications common	24% required dialysis; 50.2% developed esophageal strictures	Late complications include chronic kidney disease, esophageal strictures, and vision impairment	Esophageal stricture, late GI damage	Long-term monitoring for kidney and GI damage.	Chronic kidney disease in survivors
Balasubramanian et al. (2024)	Retrospective cohort study	Thrissur, Kerala	78 cases	Suicidal intent (80% cases); early dialysis reduces mortality	53% mortality with early dialysis, 92.1% without dialysis	Early dialysis significantly improves survival in severe cases	No data available (clinical study)	Early dialysis, sodium bicarbonate infusion.	Lower mortality with early intervention
Sujisha et al. (2020)	Prospective observational study	Trivandrum, Kerala	75 cases	Cases mainly in rubber- processing regions	85.3% developed metabolic acidosis, renal failure, haemolysis	85.3% showed renal dysfunction; common in 41–70 years age group	Glottic edema, brownish fluid in peritoneal cavity, renal failure	Postmortem toxicology assessment.	Severe renal damage common in fatalities
Sabna et al. (2016)	Prospective observational study	Kannur, Kerala	60 cases	Self-harm common in rubber-growing areas	Severe haemorrhagic gastritis, renal tubular necrosis	Renal failure, DIC, and metabolic acidosis were major causes of death	Hemolysis, renal necrosis	Supportive care, renal function monitoring.	High long-term morbidity in survivors
Datta A et al., 2024	Prospective observational study	Agartala, Tripura	42 cases	High prevalence in Tripura, India; occupational exposure common	66.7% died within 24 h of ingestion, 97.6% had stomach corrosion	Rubber latex processing acid poisoning prevalent in Tripura; high mortality from GI corrosion	Severe stomach corrosion, pulmonary congestion	Emergency intubation, fluid resuscitation, ICU monitoring.	High mortality; survivors have long-term GI issues
Bhat et al. (2014)	Case series	Sullia, Karnataka	14 cases	Accidental ingestion in low-income workers	78.5% cases were suicidal; all had orofacial burns, some GI complications	Endoscopic and supportive management improved survival rates	Severe gastric ulceration, hemorrhage	Endoscopy, oxygen therapy, haemodialysis.	Better outcomes with aggressive early treatment
Debnath et al. (2024)	Case series	Agartala, Tripura	5 cases	80% survival with intensive supportive care	1/5 cases died due to severe metabolic acidosis and shock	Metabolic acidosis and renal toxicity were common; 80% survival	Haemoglobinuria, acute renal failure leading to death	Haemodialysis, electrolyte correction, respiratory support.	Four out of five patients survived with intensive care
Vyata et al. (2020)	Case report	Manipal, Karnataka	1 case	Elderly patient; severe prognosis due to age	Single case, patient developed AKI and survived with complications	Case report: Severe metabolic acidosis, renal failure, hematemesis	GI perforation, severe systemic acidosis	Haemodialysis, ICU monitoring, metabolic correction.	Fatal case due to delayed management
Nayanatara et al. (2019)	Case report	Khammam, Telangana	1 case	GI complications predominant in older adults	Accidental ingestion led to ARDS and gastric damage, requiring gastrectomy	Late-onset complications included GI bleeding requiring emergency gastrectomy	Late-stage renal and GI deterioration	Emergency gastrectomy due to GI bleeding.	Surgical intervention improved survival chances

GI=Gastrointestinal, ARDS=Acute respiratory distress syndrome, DIC=Disseminated intravascular coagulation, AKI=Acute kidney injury

One key insight is that most fatalities are not random accidents in the workplace but intentional poisonings. This indicates that the problem is deeply intertwined with mental health and social factors in agricultural communities. Family disputes, financial stress, alcoholism, and other issues prevalent in rural life can precipitate someone to consume a readily available poison in desperation. The data from Tripura, where over half of the cases were linked to familial discord, underscore the need to frame this issue not just as an industrial safety problem but also as a social health problem. Suicide prevention efforts in these areas may need to specifically address the temptation of using easily available farming chemicals paralleling efforts in pesticide ingestion prevention.[6]

The accidental poisonings though fewer in their zone but cannot be overlooked for future abuse. The presence of three accidental ingestions among five recent cases in one series shows that unsafe handling and storage still occur. One can imagine scenarios such as children mistakenly drinking the acid or workers accidentally sipping from the wrong bottle during a long day of work. Such accidents are wholly preventable with better safety protocols.[8] The occupational angle also includes nonfatal injuries; while this review focused on fatalities, it is worth noting that every fatal case likely represents many more nonfatal incidents of acid injury (burns to skin, eye injuries, damage to the digestive tract requiring medical care). These injuries can cause lasting disability (for example, chronic swallowing difficulties from esophageal scarring) and thus have economic and quality-of-life impacts on plantation families.[11]

The regulatory review reveals that India does have laws on the books to control dangerous chemicals, but implementation in the context of a decentralized agricultural practice is challenging. It appears that in states like Tripura, formic acid is legally classified as a poison requiring licenses for sale,[12] yet dozens of cases of misuse still occurred, implying that enforcement and awareness of these regulations need strengthening. Strengthening enforcement might involve regular inspections of shops in rural areas, penalizing unauthorized sale of industrial-grade acids, and possibly providing subsidies or support for safer alternatives (so that farmers are not financially disadvantaged by using a different coagulating method). The discussion should also consider the balance between industrial/agricultural needs and safety: completely banning formic acid in rubber processing might be impractical today given its role in livelihoods, but smarter regulation and harm reduction measures could significantly lower the risks.

A promising avenue highlighted is the search for safer alternatives. The example of using buttermilk or other natural coagulants is encouraging, as it suggests that traditional knowledge or innovations can replace a hazardous practice. If these alternatives can be scaled up perhaps with technical improvements to make coagulation faster or more consistent, then the reliance on formic acid could decrease.[14] The Rubber Board’s research into mixing formic acid with other substances to use smaller quantities is also notable. In the interim, even simple changes like diluting formic acid more before distribution (so that people handle it in less concentrated form) could reduce the severity of exposure when accidents happen.[15]

Importantly, the review underlines the benefit of education and training. In every study reviewed, the authors conclude with calls for better education of those handling the acid. This is a feasible and cost-effective intervention. For instance, short training sessions can be provided when farmers purchase acid from cooperatives or suppliers, covering how to safely dilute and use it, why not to keep it in soda bottles, and what immediate steps to take if someone is exposed. Such education could be integrated into the outreach that agricultural extension officers or Rubber Board officials already perform when advising on crop practices. Community health workers in plantation areas could also disseminate this knowledge and keep an eye out for risky practices.[16]

From a clinical perspective, the discussion should note that outcomes of acid poisoning can improve with prompt and proper medical care. The high fatality rate reported is partly because many victims either do not reach the hospital in time or receive suboptimal first aid (for example, inducing vomiting which can worsen internal burns). Training local healthcare providers (at primary health centres or small hospitals in rubber-growing regions) on the management of corrosive ingestion can make a difference in survival. Some newer treatment approaches have shown to reduce mortality and complications.[8,17] Thus, alongside prevention, improving medical response is crucial for those cases that still occur.

It is also worth discussing the psychosocial aftercare. Survivors of formic acid ingestion often face long-term issues of both medical (like strictures requiring repeated dilations or feeding through gastrostomy) and psychological (guilt, depression, etc.). A comprehensive approach would ensure that survivors get rehabilitative care and counselling to prevent future attempts and to restore their health as much as possible.[11]

Relevance to primary care physicians and family medicine physicians

Primary care and family medicine physicians play a crucial role in the early detection, management, and prevention of acid poisoning cases in industrial workers. Given their proximity to affected communities, these physicians are often the first point of contact for patients experiencing acute or chronic symptoms due to acid exposure.

1. Early diagnosis and management: Recognizing gastrointestinal, respiratory, and systemic symptoms of acid poisoning is essential for timely intervention. PCPs should be aware of the occupational risks associated with rubber latex processing to guide appropriate diagnostic investigations

2. Occupational health awareness: Educating workers on protective measures and early warning signs of acid exposure can help in preventing severe complications. Physicians can also advocate for workplace safety policies

3. Long-term monitoring: Chronic exposure to acids may result in conditions such as esophageal strictures, respiratory issues, or chronic kidney disease. Regular follow-ups and preventive screenings should be part of routine care for affected workers

4. Forensic and medico-legal documentation: PCPs are often responsible for documenting clinical findings in cases of occupational poisoning, which can be crucial in forensic investigations and compensation claims

5. Public health and policy advocacy: Physicians can collaborate with public health agencies to highlight the prevalence of acid poisoning and push for safer industrial practices to reduce occupational hazards.

By understanding the forensic and toxicological aspects of acid poisoning, primary care and family medicine physicians can improve patient outcomes, advocate for worker safety, and contribute to regulatory policies aimed at reducing workplace hazards.

Conclusion

This review highlights the significant burden of formic acid poisoning in rubber-processing regions of India, emphasizing high mortality, severe complications, and the importance of early intervention. Implementing regulatory policies to restrict formic acid availability and establishing standardized treatment protocols could help mitigate the rising trend of poisoning cases.

Ethical Issues

This systematic review was conducted from the publicly available databases and hence does not require Institutional Ethics Committee Approval.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.