Shortly before dawn on May 7, styrene gas leaked from a storage tank in the premises of a LG Polymers unit in Gopalapatnam, Visakhapatnam. Within a few hours, the gas had killed 11 people and injured hundreds of others.
Styrene is a chemical compound used to manufacture plastic and rubber. It is toxic to the brain and lungs. Its minimal risk level – an estimate of daily human exposure that is likely without appreciable noncancerous health effects – is 5 ppm1. This level is far lower than the permissible exposure level mandated by the US Occupational Safety and Health Administration, of 100 ppm for an adult worker for eight hours. At 700 ppm, styrene gas becomes immediately dangerous to life and health. Considering 11 people died on the morning of May 7, the concentration of the gas that leaked was clearly very high.
Acute exposure to styrene gas causes dizziness, nausea, vomiting and breathlessness. When it comes in contact with skin and mucosal membranes, its effects include blistering and irritation. Many victims also reported a burning sensation in their eyes and a few complained of loss of vision. The gas also irritates the nose and throat, causes shortness of breath and chemical inflammation of the lung tissues. Exposure to deadly quantities of the gas can cause fluid to accumulate in the lungs2, and kill the person.
Styrene gas’s effects on the brain include a feeling of drunkenness, changes in colour vision, tiredness, confusion, and problems maintaining balance.
The possible cause of death in animals and humans is possibly asphyxia – oxygen deprivation. Autopsies should tell us more.
The International Agency for Research on Cancer (IARC) has classified styrene as a possible carcinogen. Note however that this classification is based on chronic non-lethal exposure, not on acute exposure.
Aside from its effects on humans, the leaked gas also killed birds, cattle, rats, snakes and dogs, while leaves changed colour and withered away.
Going ahead, those who were injured by the gas should be monitored for acute, intermediate and long-term effects – physical as well as psychological – and the intensity of each symptom evaluated.
To determine acute health effects bearing in mind the ways in which styrene gas is known to affect the body, public health officials will need to:
- Collect data on symptoms reported by hospitalised and non-hospitalised patients
- Clinically examine the entire body, including target organs such as the heart, lungs, skin and the nervous system
- Investigate the blood and urine
- Conduct chest X-rays and brain scans
- Conduct psychological and neurobehavioral tests
Doctors will have to determine the cause of injuries and death using clinical and autopsy information, correlated with the chemistry and toxicology of the leaked gas. And to make sure, they will also have to examine the blood and urine for the purposes of care, exposure determination and compensation. The products produced when the body metabolises styrene dissipate quickly, so these checks will have to be performed asap.
Intermediate health effects – corresponding to six months to a year from the exposure – are expected to include effects on the brain, skin and lungs effects, plus other systemic and reproductive systems. The decision on health end-points to be included can be guided by medical and toxicology studies on human and animals.
Women who were pregnant at the time of exposure or are likely to conceive in the next few months are at risk of losing the foetus, so doctors will need to monitor for foetal loss as well. Children born to those mothers who were pregnant at the time of exposure must be monitored for teratogenic effects – i.e. deformities due to toxic effects on the embryo – together with checks of normal growth and puberty, and for early development of chronic illnesses.
Finally, long-term health studies should include end-points identified from the acute and intermediate phases to determine the complete spectrum health effects. They should focus on scholastic achievement, endocrine deficiencies, reproductive capabilities, psychosocial effects, effects on the nervous system and on other systems identified from toxicological studies.
The information guiding these studies should include questions like the amount and types of toxins released, their concentration, area of spread, neighbourhoods affected, toxin seepage and persistence, and total exposure. One way to find answers is by analysing the accident in detail and modelling the gas plume’s dispersion.
Aside from children and pregnant women, the exposed population in Visakhapatnam will also include older individuals and people with comorbidities like heart, lung and other ailments, which render them more vulnerable to the effects of styrene. This population should be included in long-term studies.
Researchers may also investigate the interaction between a COVID-19 infection and the inflammatory effects of styrene gas, effects on health workers who tended to victims for potential second-hand exposure (reported in the aftermath of the Bhopal gas tragedy).
Ultimately, it’s important to establish a permanent health authority to register the exposed population – symptomatic or not – to conduct these studies as well as to continuously monitoring victims. Only by doing so can we understand all possible health effects that then inform how we care for, compensate and rehabilitate victims, and prepare for future accidents.
Consider the Bhopal tragedy itself: while researchers conducted numerous studies with the victims, they were ultimately unable to fully characterise the health effects associated with the disaster, thus sowing confusion about care of and compensation for victims. Thirty-five years later, let us not repeat the same mistakes.
V. Ramana Dhara is a professor at the Indian Institute of Public Health, Hyderabad, specialising in occupational and environmental medicine. He is a member of the International Medical Commission on Bhopal.
D. Raghunadha Rao is a medical oncologist by profession. His interests include basic, translational and clinical research, with a focus on population genetics and differences in handling environmental carcinogens.