Crop burning is the deliberate burning of agricultural leftovers, such as rice straw or wheat stubble, to clear fields quickly for the next planting cycle. Crop burning smoke can travel hundreds of miles and linger for days or weeks, depending on weather conditions.
Millions of tons of crop residue are burned annually, sending smoke into distant cities and neighboring countries (1). Agricultural fire smoke creates a recurring seasonal health problem that disrupts daily life, strains healthcare systems, and deepens the global burden of air pollution.
In the weeks leading up to crop burning season, it’s critical to make a plan to avoid exposure to smoke and airborne pollutants.
What is crop burning?
Crop burning is a fast, low-cost way to clear leftover plant material after harvest. Farmers may burn straw, stalks, or stubble directly in the field, or pile residues and burn them in one place.
For many growers, time is critical. There is often only a short window between harvest and the next planting. Burning can remove heavy residue quickly, reduce certain pests or plant diseases, and prepare fields faster than mechanical methods that require extra fuel, labor, and equipment passes.
Burns often happen in that narrow window between harvest and planting, which is why smoke shows up seasonally. Weather plays a major role, and wind can carry smoke far beyond the field, while still air can trap it closer to the ground.
Burning is efficient, but it comes with trade-offs. Some nutrients in crop residue—especially nitrogen and sulfur—can turn into gases and drift away with the smoke. Others, like phosphorus and potassium, remain in the ash, which can blow away or wash off the field before those nutrients return to the soil (2).
The science behind the smoke
When crops burn, they release a complex, invisible cocktail of pollutants.
When crops burn, they release a complex, invisible cocktail of pollutants.
At the forefront is PM2.5, particulate matter measuring 2.5 microns or less in diameter. These microscopic particles are small enough to bypass some of the body’s defenses, reach deep into the lungs, and in some cases enter the bloodstream. PM2.5 can trigger inflammation, worsen asthma, and is linked to long-term risks like lung cancer and heart disease.
Crop burning smoke can also release carbon monoxide, nitrogen oxides, and volatile organic compounds (VOCs), all pollutants that can negatively impact human health.
Studies have found links between crop burning spikes and rises in hospital admissions for respiratory diseases, including asthma (3).
Who is most at risk?
When crop burning season arrives, the health burden falls greatest on those individuals who are the most vulnerable.
Children, whose lungs are still developing, face heightened risks of asthma and stunted lung growth from prolonged exposure to PM2.5 (4). The elderly, especially those with pre-existing heart or lung conditions, see hospitalizations surge as fine particles deepen inflammation and exacerbate chronic diseases (5).
For outdoor workers, including farm workers, there’s no escaping the impact of crop residue smoke.
For outdoor workers, including farm workers, there’s no escaping the impact of crop residue smoke. Their livelihoods force them into the thick of the pollution, where every breath increases the risk of severe respiratory distress.
People with asthma and other chronic respiratory diseases can be strongly impacted by the smoke. Repeated exposure to PM2.5 from smoke aggravates asthma, decreases lung function, and is linked to premature death (6).
In urban populations downwind, particularly in densely packed cities with poor ventilation, smoke settles into a stubborn haze. Low-income communities, often lacking access to air filtration or healthcare, are hit hardest.
Where is crop burning most common?
Crop residue burning happens in agricultural regions worldwide. It tends to be most prevalent where large harvests are followed by a short turnaround to the next planting, and where residue is difficult to manage quickly with equipment, labor, or storage options.
South Asia
Burning is widespread after harvests, especially for wheat, rice, and maize stubble. Smoke can drift across borders, affecting parts of Pakistan, northern India, Bangladesh, and Nepal (7). During the post-monsoon burning season, studies estimate crop-residue burning can contribute about 30–34% of surface PM2.5 on average, and about 50–56% during plume events that transport smoke downwind toward major population centers (8).
East Asia
China has worked to curb crop stubble burning, but enforcement varies and seasonal burning persists—particularly in parts of Northeast China (9).
Southeast Asia
In mainland Southeast Asia, seasonal haze has been strongly linked to open biomass burning, a category that includes agricultural residue burning along with other burning types. One regional analysis estimated open biomass burning contributed about 57% of PM2.5 concentrations across parts of mainland Southeast Asia during the period studied.
In addition to crop residue burning, land clearing practices in countries such as Laos, Thailand, and Indonesia contribute to seasonal haze. Smoke can travel across national borders and affect neighboring countries downwind. Regional coordination has increased, and the Association of Southeast Asian Nations (ASEAN) has pledged to phase out the practice across member states (10)
Europe
Many European Union member states and the United Kingdom have strong restrictions on open burning. Even so, smoke can still drift in from neighboring countries where enforcement is weaker or where rules differ (11)(12).
United States
In the United States, agricultural burning occurs in multiple crop systems and has been identified as an understudied health concern for some rural communities, including parts of the Upper Great Plains . In EPA’s 2020 National Emissions Inventory (NEI), agricultural burning is shown as a measurable PM2.5 emissions source, with emissions concentrated in Florida, Washington, Georgia, and Horth Dakota, among others (13).
Global and local efforts to curb crop burning
The first step in preparing for crop burning season is to eliminate the smoke at its source. If farmers lack access to alternatives to residue burning and enforcement is inconsistent, there can be mitigation challenges. But there are promising solutions that combine top-down policies with grassroots adoption of new technologies.
The first step in preparing for crop burning season is to eliminate the smoke at its source.
For instance, India provides subsidies for “happy seeders,” machines that plant new crops without burning stubble. Farmers who adopted the technology were able to cut costs on land preparation, irrigation, and fuel use while still maintaining consistent, moderate crop yields (14).
China’s strict bans and enforcement via satellite surveillance helped reduce fires in key provinces like Heilongjiang (15). However, controlled fires are starting to make a comeback as some local officials are loosening restrictions. While there are companies and initiatives to pay farmers for stubble use as biofuels or animal feed, greater subsidies may be needed to support farmers due to the high supply and low demand for crop waste.
Turning waste into income offers a powerful alternative to the traditional burns. For instance, in Southeast Asia, Thailand and Vietnam are piloting programs to convert rice straw into biofuel or compost, turning waste into revenue (16) (17).
If you live downwind of agricultural regions—or you’ve seen seasonal haze before—planning ahead can reduce exposure when smoke returns.
How to protect your family and community
Stopping the fires at their source is critical. Even so, it’s essential to develop an action plan and know what steps to take before smoke begins to drift into homes and businesses.
What governments, communities, and organizations can do
- Pass legislation strongly limiting crop burning and regularly enforcing those laws.
- Support local farmers by providing subsidies for no-burn equipment and techniques.
- Push local, regional, and national officials for stricter enforcement of burning bans.
- Report violations to local environmental agencies.
- Help connect farmers with cooperatives that offer affordable rentals of no burn equipment.
What individuals can do
Before smoke arrives:
- Set up a simple monitoring routine: check PM2.5 and the Air Quality Index (AQI) regularly so you can spot poor air quality conditions early.
- Ventilate only when outdoor air is clean.
- Prep your indoor air plan: identify a “clean room” (usually a bedroom or living room) where you can keep windows closed and run a high-performance air purifier.
- If you may need to be outdoors during smoky periods, keep a well-fitted pollution mask on hand.
When smoke is high:
- Keep windows and doors closed and avoid bringing smoky air indoors.
- Reduce indoor pollution sources that add particles to the air (for example: don’t burn candles, limit frying or high-smoke cooking).
- Move exercise and kids’ playtime indoors until air quality improves.
- If you must go outside, wear a well-fitted face mask and keep outdoor time as short as possible.
- Run a high-performance air purifier consistently, especially in your clean room.
- Track conditions with an air quality monitor and an air quality app so you can adjust quickly as smoke rises or clears.
The takeaway
Push for stronger legislation and enforcement, or helping farmers adopt smokeless alternatives, there are options for helping get ahead of the annual smoke.
This harvest season, take steps to safeguard your health, stand with vulnerable neighbors, and demand systems that prioritize clean air for all.
