Being exposed to smoke from firecrackers is equivalent to smoking hundreds of cigarettes within a matter of minutes and the chemicals that the smoke contains leads to not just immediate breathing difficulties and skin irritation but, in the long term, could even raise the risk of cancer, according to several scientists.

Every year, on Diwali, the concentration of ultra-fine PM2.5 particles that contain a variety of heavy metals and toxic chemical compounds multiplies manifold between evening and the next morning as people set off firecrackers. For instance, in 2021, the PM2.5 concentration shot up from an average peak of 234 microgram per cubic metre of air (ug/m3) the night before to 729 ug/m3 at 3am after the celebrations, which included widespread use of fireworks illegally.

These are, however, average levels of recordings at monitoring stations. What they do not capture is the intensity and the effects of the acute exposure at the time of lighting firecrackers.

“We carried out a study in 2020 in Delhi to check PM 2.5 readings indoors and outdoors on Diwali day. While the outdoor concentration ranged from 1,200 to 1,400 ug/m3, indoors, where levels had been around 70-80 ug/m3 just a day before, rose to around 500 to 700 micrograms per cubic metre,” said Dr Arun Sharma, president of the Society for Indoor Environment (SIE).

India’s Central Pollution Control Board considers a PM2.5 concentration greater than 40 ug/m3 unsafe. The World Health Organization (WHO) sets the safe threshold even lower, at 5ug/m3.

Exposure to such high levels is particularly dangerous to those already suffering from diseases such as asthma and people of vulnerable age groups, like children and the elderly. But, Sharma added, this high a concentration does not even spare the healthy. “The impact on the non-vulnerable groups is seen more in the long term and often is linked to lung damage,” said Sharma.

Among the healthy, one-off firecrackers and the general citywide ambient pollution may not lead to the same harms as it does to the vulnerable, but even they are at high risk if they are close to firecrackers for long enough, said a second expert, Dr Ravindra Khaiwal, professor of Environment Health at Department of Community Medicine & School of Public Health at Post Graduate Institute of Medical Education & Research (PGIMER).

“We generally categorise people into two groups. The vulnerable group is one which consists of children, pregnant women, old people and those with comorbidities. Here, they can have short-term impacts such as irritation in the upper respiratory tract, skin infections, difficulty in breathing and severe instances of asthma. Healthy people may also see such symptoms, but it depends on the period of exposure and the dose of concentration, which is generally very high on Diwali day and can range from 500 micrograms per cubic metre, up to 1,500 micrograms per cubic metre,” he said.

A scientist from the Council of Scientific and Industrial Research (CSIR) gave a more detailed picture of the short- and potential long-term harms. “Firecrackers mainly comprise four primary ingredients—an oxidiser, fuel, colouring agents and binders—and each of these impacts human health in a different way,” said this person, asking not to be named due to the social and political divisions over the topic of firecracker use.

“Nitrates and chlorates are used most commonly as oxidisers. Aluminium compounds, barium nitrates and copper are used as colouring agents. Metals are also used to regulate the speed of reaction in various fireworks,” this person said, before explaining the ways in which such families of elements and compounds affect humans.

“Antimony sulphides, the chemical compound that results in the glitter effect, is a known carcinogen. In the short term, they trigger a feeling of nausea and in the long term, they can cause cancer. Similarly, aluminium, which burns as white light, leads to contact dermatitis and bioaccumulation. Barium nitrate and lithium compounds have the most toxic impact as they immediately cause respiratory problem.”

Khaiwal made similar warnings. “NOx (nitrous oxides) are released through firecracker emissions and nitrates can cause mental impairment. The magnesium in firecrackers can cause metal fume fever (a condition common among welders), cadmium leads to anaemia and kidney damage, zinc can cause nausea and vomiting, sodium and salts in firecrackers cause skin irritation and rash, and copper leads to respiratory tract irritation,” he said.

Khaiwal was one of the lead researchers in a study published in the Atmospheric Environment Journal titled “Long-term assessment of firework emissions and air quality during Diwali festival and impact of 2020 fireworks ban on air quality over the states of Indo Gangetic Plains airshed in India.” It found that during Diwali celebrations between 2017 and 2020, particulate matter and SO2 were the major emissions emanating from fireworks in the atmosphere.

Another way to look at the intensity of the emissions is to simply look at how much PM2.5 particles are generated in the time different firecrackers burn. A study by the Chest Research Foundation, Pune in 2016 found burning an “anaar” (a flowerpot firecracker) exposes a person standing nearby to 4,860ug/m3 of PM2.5 particles over a three-minute duration. The ubiquitous sparkler, also called “phooljhari”, releases 10,390ug/m3 of PM2.5 and a “ladi”, or a gardland of firecrackers, spews out 38,450 ug/m3 of PM2.5, equivalent to the emissions generated by 1,752 cigarettes.

A second study involving firecracker use detailed the damage from a clinical perspective. Researchers from the Department of Medicine at Maulana Azad Medical College (MAMC) interviewed 788 Delhi residents before and after Diwali in 2017, with 223 individuals also undergoing pulmonary function testing on a random basis.

“The comparison of respiratory disease complaints pre- and post-Diwali showed that there was a significant increase in complaints of cough post-Diwali among the participants of Kotla (6.7% vs. 28.9%),” said the study, led by Mradul Kumar Daga, director-professor at the Department of Internal Medicine & Centre for Occupational and environment Health at MAMC.

The study, which surveyed clusters based on neighbourhoods, found that after Diwali, people in one of these densely packed residential areas, Kotla, reported more instances of fever and fatigue. “Nearly 6.7% and 37.1% reported fever and fatigue.”

Other clinicians said their experiences were consistent with the findings. “We see coughing, wheezing immediately start in such groups on Diwali day and roughly the week after Diwali, there is a rise in the number of asthma attacks, bronchitis, pneumonia and people developing a persistent cough,” said Dr Vikas Maurya, director and Head, Pulmonology and Sleep Disorders at Fortis Hospital, Shalimar Bagh.

“When concentration is this high, these are levels that are beyond “severe” and while the vulnerable groups such as the elderly, children and pregnant women are asked to be cautious when the AQI is in the “very poor” category or worse, even healthy people are said to be impacted. It is the same case on Diwali day and all age groups are severely hit. There is a severe health emergency connected to Diwali and the spike in pollution caused by firecrackers,” said Anumita Roychowdhury, executive director, research and advocacy at the Centre for Science and Environment (CSE).