Air pollution is a major cause of death and disease. Globally, about 4.2 million premature deaths are caused by ambient air pollution. Worldwide, air pollution accounts for 29% of deaths from lung cancer, 25% of deaths from ischemic heart disease and 43% from chronic obstructive pulmonary disease.

In recent days, there has been a lot of concern over the deterioration of air quality in Sri Lanka due to the increase in the level of fine particles (PM2.5) in the atmosphere. The primary reason for the recent deterioration is said to be the entry of polluted air from the Indian subcontinent and the South Asian region at large. This movement was triggered by the cyclonic conditions prevailing over the Bay of Bengal. The elderly and the medically vulnerable had been asked to stay indoors and others were advised to wear good-quality masks.

Pre-existing Problem    
That said, air pollution has been an issue in Sri Lanka for the last two decades, not always linked to transboundary winds. In fact, air pollution has been increasing due to a variety of factors, both internal and external (transboundary). The phenomenal growth of vehicular traffic, the use of fossil fuels for power generation and the use of wood and biomass as fuel have also been causes. This has been brought out by Peradeniya University Science Faculty’s O.A. Ileperuma in his Review of Air Pollution Studies in Sri Lanka published in 2020. 
Here are some of the takeaways from Ileperuma’s review:

Air pollution refers to the release into the atmosphere of various gases and fine particles at rates that exceed the natural capacity of the environment to dissipate, absorb and dilute. The gaseous air pollutants of primary concern are sulphur dioxide, nitrogen dioxide and carbon monoxide which are directly emitted owing to the combustion of fossil fuel in automobiles, power plants, industries and biomass burning. Ozone formed in the lower atmosphere is a secondary air pollutant generated from the photochemical reactions of primary air pollutants like NO2 (Nitrogen Dioxide). Diesel smoke consists of unburnt hydrocarbons like poly-aromatic hydrocarbons which are known carcinogens.

Fossil fuel combustion yields fine particles that can penetrate deep into  the lung. An average person inhales about 10,000 litres of air daily. Therefore, its purity profoundly affects people’s health. 

In Sri Lanka, there are no long-term epidemiological studies carried out to assess the outcome of health effects due to air pollution. But several brief reports on the health effects are available. Pollution levels are highest during the North-East Monsoon months (December to February) owing to transboundary air pollution. During the period 1997-2003, levels of sulphur dioxide, nitrogen dioxide, and ozone were steadily increasing while those of carbon monoxide levels were decreasing.

Air pollution increase in Sri Lanka is also due to the phenomenal increase in the number of motor vehicles, traffic congestion, the increasing use of fossil fuel for power generation and also the continued use of wood in domestic cooking and the use of biomass in the rural areas. During the period of an acute shortage of cooking gas, many households in metropolitan Colombo also switched to wood for cooking.     

Air quality in the hill town of Kandy is worse than that of Colombo owing to its geographical location. In Kandy, sulphur dioxide, nitrogen dioxide and ozone levels exceeded the standards on 41%, 14% and 28% of the occasions during the period 2001-2005. Due to the polluted air, there are increasing cases of respiratory diseases such as chronic obstructive pulmonary disease in Kandy. 

Industrial and Vehicular Pollution  
In 2011, emissions from motor vehicles accounted for 55-60% of air pollution, while 20-25% was due to industries and 20% was from domestic sources according to the Sri Lankan Ministry of Environment. 

Sri Lanka once produced over 95% of its power needs from hydel projects, but this has gradually decreased, with hydropower now accounting for only about 50% and sometimes even less. In 2018, the generation mix from hydro, thermal and coal was: 5,149, 1,886 and 4,764 GWh respectively (according to a Central Bank report of 2018). Thus, more power was produced by burning fossil fuels creating more pollution. 

Colombo city’s air is polluted because 50% of the vehicles, 70% of industries and several thermal power plants are located in the Colombo Metropolitan area.  

The transport sector generates the most amount of air pollution. The biggest increase is in the number of motorcycles, which account for about 50% of the entire vehicles fleet. The vehicle fleet in Sri Lanka increased from 978,544 in 1997 to 8.1 million in 2019. Nearly 50% of all vehicles are registered in the Western Province, the most highly populated and congested of the Provinces. Vehicles using two-stroke engines were bad pollutants.

The phenomenal increase in the number of motor vehicles has resulted in traffic jams. And traffic jams produce more soot, carbon monoxide and unburnt hydrocarbons compared to vehicles travelling smoothly at a uniform speed of about 40 km/h.

The uncontrolled increase in the number of vehicles will be the biggest challenge in the future. The economic loss due to traffic congestion in Colombo has been estimated by Prof. A. S. Kumarage of Moratuwa University, to be around Rs.32 billion annually. The increased cost of treating patients affected by air pollution will be an immense economic burden to the government.

Mitigating Measures
Under the Clean Air Action Plan of 2000 and subsequent plans in 2007 and 2015, several measures to reduce air pollution in Sri Lankan cities have been taken. These include lowering sulphur in fuel from 0.5% to 0.25%; banning two-stroke three-wheelers; terminating the addition of lead to petrol and commencing the Vehicle Emissions Testing programme. 

These have had a beneficial impact. However, so long as fossil fuels are the predominant source of energy and the number of petrol and diesel vehicles on the road is not controlled, the air in Sri Lanka will remain polluted above safe levels.  The future is none too bright as there is no sign yet of public transport replacing or minimizing private transport, and the railways replacing road transport to minimize air pollution.