Holidays are generally supposed to be fun. But big celebrations can sometimes bring big risks. Massive fireworks displays delight the eye, for instance. They also can fill the air with pollution that hangs around for hours or more. It’s something that people in India had long suspected. Last year, data emerged showing that fireworks bring choking pollution to many people, here, during the festival of Diwali.
This annual four-day Hindu religious celebration commemorates the triumph of good over evil, knowledge over ignorance — and light over darkness.
After the main day of revelry, people celebrate by setting off firecrackers. They can do it all night long. On the day after last year’s Diwali fireworks, people in New Delhi, India’s capital city, awoke on November 7 to especially dirty air. The levels had spiked overnight, starting around when the fireworks began. And in an urban area that is home to 29 million people, a lot were affected.
What’s more, data from the 2018 Diwali festival were no fluke.
A study that came out last August turned up a recent, consistent trend. It linked Diwali fireworks in the Indian capital to short term — but extreme —air pollution. Indeed, the authors of that study concluded: “To our knowledge this is the first causal estimate of the contribution of Diwali firecracker burning to air pollution.”
For 15 years, a growing body of research had raised concerns about such pollution.
Balram Ambade was one of those concerned scientists. He is a chemist at the National Institute of Technology in Jamshedpur, India. Last December, he presented data on particulate matter (or PM) from Diwali fireworks in his city. Scientists measure such pollution in micrograms per cubic meter (μg/m3) of air. In a 12-hour period on the holiday, PM values soared to 500.5 μg/m3. That rise was about 21 to 27 percent higher than before the fireworks went off.
A series of such studies had prompted India’s 31-member Supreme Court to pass a new ban on fireworks last year. Only “green” fireworks could be sold leading up to the holiday.
India’s Council of Scientific and Industrial Research has been working to create these more environmentally friendly fireworks. They emit less pollution. Still, they are not pollution-free. So even these approved fireworks could only be set off between 8 and 10 p.m., the court ruled.
Despite such a rule, India found it hard to enforce the ban. Many people still set off firecrackers. And air monitoring stations around New Delhi showed that PM levels spiked overnight from November 6 to 7. Amounts of the smallest and most risky particles, known as "fines," topped out at nearly 250 μg/m3 — a whopping 150 μg/m3 above normal.
Focusing on ‘fine’ particles
Dhananjay Ghei at the University of Minnesota in Minneapolis teamed up for a related but longer study with Renuka Sane at the National Institute of Public Finance and Policy in New Delhi.
At the best of times, India’s capital tends to be one of the world’s most polluted, they note. Its air is dirtiest from October to January. It’s PM pollution is a mix of sooty and metallic bits and tiny liquid droplets. Each can be so small that it hangs in the air for hours, days — sometimes even for weeks.
The burning of fossil fuels — coal and oil — is a major source of PM. And the smaller that those particles are, the more deeply they can enter the lungs, causing harm. So the most harmful particles are those fines. Being 2.5 micrometers in diameter or smaller, they also are known as PM2.5.
Tailpipe emissions from cars and trucks are a major source of fine-size PM. That’s why in India’s capital, levels of these pollutants rise during the morning commute, then fall around lunchtime. They surge again in the evening as people drive home from work.
What Ghei and Sane wanted to know was whether fireworks intensified New Delhi’s fine pollution. To find out, they focused on PM2.5 data from four sites across the city.
Accounting for seasonal changes
One challenge: Diwali does not occur on the same date, each year. Based on a lunar calendar, it moves from year to year between October and November. Sometimes it occurs at the same time that farmers burn harvest wastes. Other times it does not. The researchers used hour-by-hour data from four straight years to see if they could tease out whether fireworks, crop burning or something else could explain the very dirty air seen during Diwali.
They looked over data from the week before Diwali through the days right after it. And they looked at precisely when and how PM levels changed during that period. They were hunting changes that coincided with the fireworks revelry.
And they found some.
Overall, “We find that Diwali leads to a small, but statistically significant increase in air pollution,” Ghei and Sane reported. How big that increase was varied across the four sites. It also varied some by the year (2013 to 2016).
The data did not show that fireworks just took take place at dirty times of the year. Instead, they showed that fireworks are partly to blame for making the air unhealthier than normal.
Of course, what Ghei and Sane call a “small” rise may be viewed differently by other air pollution experts. The Diwali effect they found was an increase of roughly 40 μg/m3. As they note, this is on top of “a base of already high pollution” at that time of year in the Indian capital — potentially hundreds of μg/m3. For perspective, U.S. law prohibits PM2.5 levels that are higher than 35 μg/m3 for longer than 24 hours. In fact, the U.S. limit falls to a mere 12 μg/m3 for periods longer than a day.
So these researchers observed an uptick in pollution that would have turned even super-clean air unhealthy. Diwali's bonus pollution was arriving at a time of year when the city’s air was not super clean.
Ghei and Sane described their data in the August 1, 2018 issue of PLOS ONE.
Plenty of other sites see fireworks pollution, too
Some places in China, the home of fireworks, also see sharp spikes in pollution after big celebrations. One 2017 study, for instance, found a 4- to 6-fold boost in air pollution within four hours of fireworks. And pollution levels didn’t fall back to normal for two to three days. Or so reports a team led by Yang Song of Shandong University in Jinan, China.
India’s capital city is not the only one to suffer a Diwali effect. Tirthankar Banerjee is an atmospheric physicist. He works at Banaras Hindu University in Varanasi where in 2014 he led a local study. Equipment on his university campus measured all sorts of air pollutants every four hours in the days leading up to and through the 2014 Diwali festival. Fine PM levels spiked after the fireworks. At the same time, the team saw a similar rise in certain metals used in fireworks. Those metals appeared to mark this pollution as coming from the fireworks, the team reported in 2016.
Last year, scientists used similar tracers to confirm a link between a spike in fine pollution in the air over South Korea and distant lunar New Year’s celebrations in China.
Pollution can become an important issue even for U.S. cities around the 4th of July. Dian Seidel led one research team that investigated this. At the time, she worked for the National Oceanic and Atmospheric Administration in College Park, Md. She and a colleague scoured hourly data on PM2.5 levels collected before and during the Independence Day celebrations between 1999 and 2013.
Pollution rose dramatically in the hours during and after the fireworks, they noted in a 2015 paper. In Ogden, Utah, for example, levels of PM2.5 peaked after one July 4th fireworks display at almost 500 μg/m3. Fortunately, it didn’t hang around.
Still, the monitoring site in Ogden, Utah was right next to the fireworks display. As such, the authors point out, the high pollution values seen there “may be more representative of exposure to spectators than results from other sites.”
Dan Satterfield is a meteorologist who blogs about pollution for the American Geophysical Union. He described one 4th of July event in Washington, D.C., a few years ago.
“The smoke was so bad on the Mall that you could not see the end of the show!” he wrote. “The air quality sensors across the country always show a big bump on the evening for the 4th.” On this year, he pointed out, an early evening thunderstorm helped to trap fireworks pollution low to the ground.
How toxic is fireworks pollution?
According to the U.S. Environmental Protection Agency, PM pollution can harm your lungs and your heart. Studies have shown such pollution can cause early deaths in people with heart or lung disease, the agency's website notes. PM also can trigger nonfatal heart attacks. It can make someone’s asthma worse. And it can irritate the lung's airways, making it hard to breathe. People facing the biggest health risks from this pollution are children, the elderly and those with heart or lung disease, EPA warns.
But certain aspects of fireworks PM may pose special risks, Banerjee says. “Emissions from fireworks are very important as they potentially emit a huge amount of metals,” he says, “which are mostly carcinogenic.” In addition, he notes, for very short periods, the mix of fireworks pollutants can build to “exceptionally high” levels. At this point, he told Science News for Students, “You know, it becomes tough to even breathe.” The problem: Young people enjoy going to fireworks festivals, he says, "without knowing the [risks].”
annual Adjective for something that happens every year. (in botany) A plant that lives only one year, so it usually has a showy flower and produces many seeds.
asthma A disease affecting the body’s airways, which are the tubes through which animals breathe. Asthma obstructs these airways through swelling, the production of too much mucus or a tightening of the tubes. As a result, the body can expand to breathe in air, but loses the ability to exhale appropriately. The most common cause of asthma is an allergy. Asthma is a leading cause of hospitalization and the top chronic disease responsible for kids missing school.
colleague Someone who works with another; a co-worker or team member.
concentration (in chemistry) A measurement of how much of one substance has been dissolved into another.
diameter The length of a straight line that runs through the center of a circle or spherical object, starting at the edge on one side and ending at the edge on the far side.
Environmental Protection Agency (or EPA) A national government agency charged with helping create a cleaner, safer and healthier environment in the United States. Created on Dec. 2, 1970, it reviews data on the possible toxicity of new chemicals (other than foods or drugs, which are regulated by other agencies) before they are approved for sale and use. Where such chemicals may be toxic, it sets limits or guidelines on how much of them may be released into (or allowed to build up in) the air, water or soil.
fossil fuel Any fuel — such as coal, petroleum (crude oil) or natural gas — that has developed within the Earth over millions of years from the decayed remains of bacteria, plants or animals.
green (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.
heart attack Permanent damage to the heart muscle that occurs when one or more regions of it become starved of oxygen, usually due to a temporary blockage in blood flow.
lunar Of or relating to Earth’s moon.
metal Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure).
meteorologist Someone who studies weather and climate events.
micrometer (sometimes called a micron) One thousandth of a millimeter, or one millionth of a meter. It’s also equivalent to a few one-hundred-thousandths of an inch.
National Oceanic and Atmospheric Administration (or NOAA) A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.
particulate A tiny bit of something. A term used by pollution scientists to refer to extremely tiny solid particles and liquid droplets in air that can be inhaled into the lungs. So-called coarse particulates are those with a diameter that is 10 micrometers or smaller. Fine particulates have a diameter no bigger than 2.5 micrometers (or 2,500 nanometers). Ultra-fine particulates tend to have a diameter of 0.1 micrometer (100 nanometers) or less. The smaller the particulate, the more easily it can be inhaled deeply into the lungs. Ultra-fine particulates may be small enough to pass through cell walls and into the blood, where they can then move throughout the body.
physicist A scientist who studies the nature and properties of matter and energy.
policy A plan, stated guidelines or agreed-upon rules of action to apply in certain specific circumstances. For instance, a school could have a policy on when to permit snow days or how many excused absences it would allow a student in a given year.
pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly. (in biology) The structure that an organism uses to sense attributes of its environment, such as heat, winds, chemicals, moisture, trauma or an attack by predators.
smoke Plumes of microscopic particles that float in the air. They can be comprised of anything very small. But the best known types are pollutants created by the incomplete burning of oil, wood and other carbon-based materials.
soot Also known as black carbon, it's the sometimes oily residues of incompletely burned materials, from plastics, leaves and wood to coal, oil and other fossil fuels. Soot particles can be quite small — nanometers in diameter. If inhaled, they can end up deep within the lung.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
urban Of or related to cities, especially densely populated ones or regions where lots of traffic and industrial activity occurs. The development or buildup of urban areas is a phenomenon known as urbanization.
waste Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.
Data Source: Delhi Air Pollution. Air Quality Index CN. Accessed 6 November 2018
Visualization of current PM2.5 values across the planet: Air Visual Earth
Journal: B. Ambade. The air pollution during Diwali festival by the burning of fireworks in Jamshedpur city, India. Urban Climate. Vol. 26, December 2018, p. 149. doi: 10.1016/j.uclim.2018.08.009.
Journal: D. Ghei and R. Sane. Estimates of air pollution in Delhi from the burning of firecrackers during the festival of Diwali. Plos ONE. Vol. 13, Aug, 13, 2018, p. e0200371. doi: 10.1371/journal.pone.0200371.
Book chapter: P.C.S. Devara et al. Anomalous features of black carbon and particulate matter observed over rural station during Diwali festival of 2015. Environmental Pollution. In: V. Singh, S. Yadav, R. Yadava (eds) Environmental Pollution. Water Science and Technology Library, Vol 77. Springer, Singapore; 2018. p. 293–308. doi: 10.1007/978-981-10-5792-2_24.
Journal: Y. Song et al. The characteristics of air pollutants during two distinct episodes of fireworks burning in a valley city of North China. PloS ONE. Vol. 12, January 3, 2017, p. e0168297. doi: 10.1371/journal.pone.0168297.
Journal: M. Kumar et al. Fireworks induced particle pollution: A spatio-temporal analysis. Atmospheric Research. Vol. 180, November 1, 2016, p. 78. doi: 10.1016/j.atmosres.2016.05.014.
Journal: D.J. Seidel and A.N. Birnbaum. Effects of Independence Day fireworks on atmospheric concentrations of fine particulate matter in the United States. Atmospheric Environment. Vol. 115, August 2015, p. 192. doi: 10.1016/j.atmosenv.2015.05.065.
Journal: B. Thakur et al. Air pollution from fireworks during festival of lights (Deepawali) in Howrah, India—a case study. Atmosfera. Vol. 23, 2010, p. 347.
Journal: N.D. Ganguly. Surface ozone pollution during the festival of Diwali, Delhi, India. Earth Science India. Vol. 2, October 2009, p. 224.
Journal: S.C. Barman et al. Ambient air quality of Lucknow City (India) during use of fireworks on Diwali Festival. Environmental Monitoring and Assessment. Vol. 137, February 2008, p.495. doi: 10.1007/s10661-007-9784-1.
Journal: U.C. Kulshrestha et al. Emissions and accumulation of metals in the atmosphere due to crackers and sparkles during Diwali festival in India. Atmospheric Environment. Vol. 38, September 2004, p. 4421. doi: 10.1016/j.atmosenv.2004.05.044.
Data source: Atmospheric Soundings. University of Wyoming. Accessed November 7, 2018
Explainer: Air Quality Index: A Guide to Air Quality and Your Health. U.S. Environmental Protection Agency. February 2014
Tweet: ANI. @ANI. Twitter. 7 November 2018
Tweet: Robert Rhode. @RARhode . Twitter. 31 October 2018
News report: M. Cappucci. Air pollution skyrockets to hazardous levels in India. The Washington Post. November 8, 2018.
News report: S. Tandon. India’s supreme court allows firecrackers for Diwali, but with riders. Quartz India. Oct. 23, 2018.
News report: M. Safi. India’s supreme court bans Diwali fireworks in Delhi to tackle pollution. The Guardian. October 9, 2017.
News report: Delhi pollution: Government issues health advisory as smog chokes city. Hindustan Times. November 8, 2016.
News report: A. Ghosal and P. Chatterjee. Landmark study lies buried: How Delhi’s poisonous air is damaging its children for life. The Indian Express. April 2, 2015.