Burning green: Health costs of landscape fires
The cascading effects of forest fires and stubble burning on human health and environment are severe
A recent report in The Lancet estimated that, globally, around 1.53 million excess deaths occurred each year during 2000-19 due to smoke from “landscape fires”, a term for forest fires and dry vegetation, including planned farm fires. The study correlated deaths to exposure to particulate matter (PM) 2.5 and ozone. Cardiovascular deaths contributed 0.45 million and respiratory diseases 0.22 million to this annual toll of where life was snuffed out by the “burning green”.
Forest fires have been in the news over the past few years. They attained notoriety for devastating vast tracts of land in North America and Europe, destroying homes and businesses, and displacing thousands of people. The Canadian wildfires of 2023 broke records and involved all 13 provinces and territories. As smoke from Canada wafted across the border into the US, people living in upper midwestern states realised that neither walls nor tariffs by presidential decree could keep their health and economy protected from wildfires raging in their neighbour’s forests. The smoke from Canada even reached Europe. California, of course, has its annual ordeal by forest fire, with high levels of damage and displacement. As of November 25, 2024, a total of 7,818 wildfires have burnt down 1,044,126 acres in the American state this year. In Greece, the wildfires of August 2024 scorched 100,000 acres of land.
The US leads the list of countries on economic damage from wildfires, with Indonesia, Canada, Portugal, and Spain following. A 2022 report by the United Nations Environment Programme (UNEP), Spreading Like Wildfire: TheRising Threat Of Extraordinary Landscape Fires, highlighted the danger posed by a combination of the climate crisis and land use change, with an anticipated increase in landscape fires even in regions of the world that were hitherto unaffected.
According to recent estimates, nearly 36% of India’s forests are at risk of wildfires. States with high forest cover (such as Odisha, Chhattisgarh and those in the northeast) are at high risk. Burning forests is sometimes adopted as an easy way to clear land for agriculture, real estate, or industry. Apart from forest fires, burning crop waste has been an annual hazard that contributes to high levels of pollution in northern India.
Forest fires have a highly damaging impact on human health. Smoke emanating from the burning of dried forest vegetation contains a dangerous cocktail of toxic chemicals. Their inhalation introduces them to our lungs and, from there, to the bloodstream. This leads to an assault on various tissues in the human body. They also irritate the conjunctiva of the eyes and exposed skin. Together, these chemicals cause widespread inflammation and spike up oxidative stress through free radicals. They can cause thrombosis (blood clotting) by triggering pathways of coagulation and platelet activation, blood sugar (dysglycaemia) and blood fat (dyslipidemia) disorders, apart from depressing immunity. They can damage genes, altering their structure and functions through harmful mutations.
PM2.5, carbon dioxide, ozone, aromatic compounds, and nitrogen dioxide attack the lining of the blood vessels and promote blood clotting, leading to paralytic brain strokes, heart attacks, pulmonary embolism, electrical disturbances in the heart (arrhythmias), respiratory disease, pre-diabetes, and diabetes. Prolonged exposure can also cause cognitive dysfunction. Fine particulate matter is particularly abundant in the smoke which emanates from the combustion of vegetation. In addition to these provocateurs of inflammation, benzene and formaldehyde, which are released from the combustion, can cause cancers through mutagenesis.
Cardiovascular events are most common among elderly persons exposed to environmental smoke from burning vegetation or wood burnt in house fires. Three principal mechanisms have been identified: Modulation of autonomic balance and neural input into the heart, the release of pro-inflammatory mediators by irritated lungs leading to widespread systemic tissue inflammation, and the penetration of particulate matter into blood circulation.
Acute PM2.5 exposure, with resultant autonomic stimulation, increased coagulability of blood, and inflammation can trigger heart rhythm abnormalities, heart attacks and exacerbated heart failure in those already having heart disease. In persons with atherosclerotic plaques in their arteries, exposure to high levels of PM2.5 can cause these plaques to become “unstable” and even rupture and trigger blood clotting — leading to acute, unheralded heart attacks and sudden death.
While extreme heat or lightning can spark forest fires by igniting dry leaves and twigs, humans too may trigger them by carelessly discarding unextinguished cigarettes or beedis, lighting campfires, or cooking fires that leave behind burning embers. Such careless acts not only harm human health but also take a toll on forest-dwelling animals while depleting the biodiversity of plant life. If the climate crisis has been mostly anthropogenic, thanks to collective human follies over several decades, such acts of arson are instantaneous acts of criminality that must be curbed through public education and behaviour change.
During landscape fires, human health must be protected from air pollution (smoke) and dehydration (heat). Those who are at high risk of adverse health effects (elderly persons and those with pre-existing heart or lung disease or diabetes) must wear N-95 masks for protection against particulate matter and noxious gases. Those at highest risk should stay indoors and use air filtration devices. Maintaining adequate hydration is vitally important to reduce the risk of blood clotting and soothe inflamed body tissues. While we do this, we must also soothe our inflamed planet by working on slowing down the pace of climate change and applying the brakes on global warming.
K Srinath Reddy is distinguished professor of public health, PHFI, and the author of Pulse to Planet.The views expressed are personal
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