Since the beginning of October, a thick brown smog has shrouded Northern India and Pakistan. To residents, it’s a familiar sight: “Parali” season, or stubble-burning, has begun.
During the fall, farmers set fire to bare stalks of harvested crops to clear the land for the following season’s cultivation. As these agricultural fields burn, regional air pollution spikes to “very unhealthy” and “hazardous'' levels, often for days or weeks at a time.
Pictured: Delhi and Lahore top the Major City Ranking for worst air pollution globally on 9 November, at 8:00am (MST). The severe air pollution levels in these two cities is largely attributed to agricultural fires.
On 10 November at 10:30 AM, Delhi’s air quality index (AQI) reached a record high for the season: 1092. PM2.5(particulate matter with a diameter size of 2.5 microns or smaller)concentration levels at this time measured 813 micrograms per cubic meter (μg/m3), roughly 32 times the World Health Organization (WHO) target for daily exposure (25 μg/m3).
Pictured: Hourly air quality index (AQI) levels reach 1039 on Tuesday, November 10.
As of mid-November 2020, as many as 4,000 agricultural fires were burning at any given time in the 409 km (254 mi) stretch between Delhi, India and Lahore, Pakistan. The region, which spans Punjab and Haryana province, is known as India’s agricultural “breadbasket.” Farms here alternate between two harvesting seasons: a winter wheat crop reaped in April and May and a summer rice crop reaped in October and November.1
Harvesting the fall’s rice crop is most often associated with open burning. This is because mechanized rice harvesters tend to leave behind a significant amount of waste. In order to prepare the fields for the next sow in a few short weeks, farmers resort to burning the remaining residue.
In 2020, fires commenced around mid-October. Since then, air quality levels in the region have remained “very unhealthy” or worse. This air quality designation indicates that all 50 million residents exposed are likely to experience some adverse health effects as a result.
The stubble burning season of 2020 has already greatly exceeded the 2019 season. Between 1-23 October, a total of 11,796 fires burned in Punjab as compared to just 4,889 fires during the same period in 2019.2 This year, a much larger area was harvested, hence the increase in fires.
Why is crop burning such a major air quality concern?
At first glance, crop burning can appear to be an atrocious but preventable air quality concern.
But from a farmer’s perspective, stubble burning not only shortens and eases the transition to the next season but also rids the land of pests and weeds and returns plant-stored nitrogen back to the soil. In an industry where margins are thin, schedules must be kept, and time is money, the convenience and cost savings afforded by crop burning supersedes all else.
But these short-term economic benefits come at a high cost to the environment and human health. Worldwide, open burning represents the leading cause for air pollution-related illness in outdoor environments and contributes significantly to climate change.3
Why is Delhi so polluted?
Delhi has the reputation of having some of the world’s worst air quality, even without the impact of crop burning in November.
In 2019, Delhi was ranked the most polluted capital city in the world, with an annual PM2.5 concentration of, 98.6 μg/m³, nearly 10 times the World Health Organization annual exposure target of 10 μg/m³. While November, peak stubble burning season, is typically the city’s most polluted month, averaging a PM2.5 concentration of 200.7 μg/m³ in 2019, high pollution levels tend to be sustained through January, well after the Pawali season is over.
Pictured: Yearly and monthly PM2.5 averages across major cities in Pakistan and Northern India.
India’s SAFAR (System of Air Quality and Weather Forecasting and Research) program estimates that smoke blown into Delhi from agricultural farms only contributes to roughly 20-40 percent of Delhi’s city-wide emissions on any given day in Pawali season.4
Other sources of Delhi’s pollution mix include:
- transportation emissions
- biomass burning for household cooking and heating
- coal combustion
High wintertime air quality levels are not simply indicative of emissions alone. Delhi’s geography and weather often play a role by preventing normal emission dispersion.
The rice harvest season coincides with post-monsoon conditions that stagnate air. During winter, the average wind speed in Delhi varies between 1-3 m/s, roughly one third slower than average summer speeds. Winds are typically considered the most powerful weather condition for dispersing air pollution. Without winds to carry pollutants away, emissions accumulate in the valley and pollution levels rise.
Making matters worse is Delhi’s geographic location in a “bowl” surrounded by mountains. As coastal winds blow in, they become trapped by the foothills of the Himalayas, with only a narrow outlet to escape. Notoriously polluted cities, Beijing, China and Los Angeles, California, have similar geographic conditions to these.
The combination of unideal conditions result in Delhi’s frequently unhealthy air quality. In 2019, 60.5 percent of hours in Delhi were classified as “unhealthy” or worse, with 7.8 percent deemed “hazardous.” Only 1.1 percent of hours were deemed to have “good” air quality.
As a result of such severe and unrelenting pollution levels, it is estimated the city suffered a loss of 41,000 deaths annually and at least $6 billion in economic costs from January to November 2020.
What are the health impacts of crop burning pollution?
Agriculture is an essential industry, but commercial crop production can have negative impacts on human health. In countries like India and Pakistan, crop burning is a primary contributor to poor air quality and can be very detrimental to human health.
A 2019 study in the International Journal of Epidemiology found that people living in northern India, where stubble burning was most common, experienced a three-fold higher risk of acute respiratory infection.5 Children under the age of 5 were especially found to be at risk.
Exposure to these pollutants can have numerous short-term effects, such as:
- coughing and wheezing
- upset stomach
- chest pain and tightness
- shortness of breath
- lung, eye, throat, and nose irritation
- irregular heartbeat
- increased risk of respiratory infection
- more frequent and intense asthma attacks
Longer-term health effects of exposure to crop burning pollution may include:
- respiratory illness and chronic lung disease
- neurological disease
- chronic obstructive pulmonary disease (COPD)
- increased carcinogenesis risk
- change in lung function
- cardiovascular illness
- premature death
Crop burning also contributes high concentrations of toxic air pollutants, including:6
What are Delhi & Lahore doing to curb crop burning pollution?
2019 marked the first year of India’s National Clean Air Program (NCAP), a roadmap for tackling air pollution through monitoring, regulation, and enforcement. Major targets include reducing PM2.5 pollution by 20-30% in key cities by 2024 (as compared to 2017 levels).7
The state of Punjab has long banned stubble-burning, but enforcement has been lack-luster.
Prompted by exceedingly high pollution levels in the Delhi-NCR region, the central government announced it would dissolve the Environment Pollution (Prevention and Control) Authority (EPCA) on 29 October and replace it with the Commission on Air Quality Management in the jurisdiction of the Punjab, Haryana, Rajasthan and Uttar Pradesh provinces.8
This new commission has been encouraged to take all measures necessary to stop stubble burning and improve regional air quality. Non-compliance with the new Commission’s measures will result in a maximum jail sentence of five years, a high fine, or both.
Even in the face of such severe penalties, however, stubble burning continues unabated. Farmers have protested that they lack financial incentives to make a switch to cleaner waste management practices.
The Punjab government has attempted to incentivize farmers to reduce this practice by, for example, offering 27,000 stubble removing machines. To date, only 14,000 have been distributed. More incentives are likely needed for cooperation, as farms (especially small-scale farms) lack resources for making the transition alone.
With government incentives and rebates as well as fines and penalties, the Commission is hopeful that emissions can be driven down. However, it may take years before farmers are able to transition to environmentally-friendly waste management practices.
Some progress has been made. As compared to 2018, 2019 saw improvements in PM2.5 concentrations across all Indian cities (except for in Nagpur). These reductions, however, appear to be more attributable to economic slowdown and favorable meteorological conditions than air pollution mitigation measures.
It’s unclear whether improvements in air quality will continue. The lockdown measures due toCOVID-19(a serious disease, often fatal, that is caused by the SARS-CoV-2 virus) during the spring of 2020 resulted in short-term improvements to air quality. However, the fall of 2020 has already experienced a 240 percent increase in stubble burning as compared to 2019. Such a sharp increase in agricultural fires could jeopardize overall improvements for the year.
However, many other countries have also worked to outlaw crop burning.
Crop burning illegal England, Wales, and China.9,10 The practice is banned in the European Union except for plant health reasons and discouraged in Australia.11,12 It is allowed in Canada by permit and in the United States, though it is regulated in certain states and tribal governments with Smoke Management Programs.13,14
Many farmers in India, Pakistan, and around the world are aware that their practices contribute to poor air quality. However, many believe they have little choice in the matter – they simply can’t afford to rid themselves of excess straw by other means.15
A number of conservation agriculture mitigation measures have been proposed to reduce burning in the region that may be possible in other countries as well, including:16
- zero-tillage agriculture
- biomass used as animal feed
- biomass-based thermal power plants
- mushroom cultivation
With a combination of legislation and new agricultural practices, progress is possible in reducing and ultimately ending the poor air quality linked to crop burning for good.