While most people link air pollution only to burning fossil fuels, other activities such as agriculture and biomass burning also contribute to it. The complexity of air pollution can be explained by analyzing the composition of the PM2.5, one the most important air pollution indicators.
PM2.5 is a fine particle matter with an aerodynamic diameter equal to or less than 2.5 microns (20 to 100 times smaller than the human hair) which causes a broad range of health effects, especially to the respiratory and cardiovascular systems. Primary PM2.5 particles are directly emitted from sources such as dust from construction sites, or biomass or fossil fuel burning. Secondary PM2.5 particles are produced through chemical reactions in the atmosphere of precursory substances, mainly SO2, NOX, together with NH3. These substances are emitted from the same sources of primary PM2.5 and from the production and use of mineral fertilizers, storage and application of livestock waste, and industrial production from certain sectors. PM2.5 can stay in the air for weeks and, thus, travel 500 km or more from the source of emissions. A dramatic example is the 2015 heavy air pollution in Southeast Asia downwind from the fires in Indonesia.
For many years, the overwhelming importance of the climate change agenda and the drive to decrease carbon emissions have resulted in an oversimplification of the challenges of achieving clean air and an overarching focus on primary PM2.5. While the dynamic and impacts of carbon emissions and air pollutants have synergies, it is important to recognize that they are not the same, and at times, can be conflicting.
A clear example is the push from many European countries for diesel vehicles over the past 20 years, which have been portrayed as “clean.” While it is true that diesel vehicles emit 15-20% less CO2 than similar gasoline vehicles, it is also true that they emit about 20 times more NOX than gasoline vehicles with a mandatory catalyst. The recent problems faced by Volkswagen and Mitsubishi underscore the difficulty of decreasing NOX emissions from diesel vehicles to meet NOX emission standards.
The initial focus on primary PM2.5 in Europe has improved air quality, but secondary PM2.5 now represents up to 70% of the aggregate PM2.5 in the atmosphere, and any additional improvement in air quality must now focus on the precursory substances of secondary PM2.5. In fact, the UK and France now consider removing incentives related to diesel vehicles as an effort to meet the EU 2020 air quality standards.
So, what do steak and fries have to do with this? Let us look at the case of the Paris smog crises in March 2014 and March 2015. In France, only 10% of the power is generated from fossil fuels. Meanwhile, France has a strong agricultural sector and 97% of its NH3 emissions come from agriculture, including livestock. In both years, strong thermic inversion with mild temperatures and low wind speeds during the application of spring fertilizer (based on manure) led to high levels of NH3 emissions. These emissions reacted with NOX and condensed into atmospheric particulate matter (PM) creating the heavy smog which covered the city. The emergency measures adopted for several days focused on restrictions on transport, but the situation improved only when a weather front with fast wind arrived.
In general, governments try to address air quality issues with specific actions aimed mainly at restricting urban traffic and/or fossil-fuel power plants in a city. This limited view is a challenge that the Bank is already facing as more countries seek its support to address air pollution issues.
For instance, the Government of China recently asked the Bank to support the Province of Hebei in its effort to improve air quality. The initial discussions focused only on decreasing coal consumption on power plants and increasing the number of electric vehicles in cities. NH3 data and rural emissions were not included in their initial analysis and thus, we spent time early on bringing experts to Hebei and sharing data to explain the complexity of the air quality agenda. Once Hebei and Bank teams got a fuller picture of the issues, we jointly defined a multi-sectoral Program-for-Results focusing on air quality management which includes controlling industrial, agricultural, and vehicular emissions and promoting the use of clean stoves. The Program, approved by the Board in June 2016, also includes the adoption of planning and management tools which consider meteorological data, cost-effectiveness measures and synergies with the climate change mitigation agenda in the region.
There is no need for extreme measures like cutting steak and fries from your diet (at least not on the account of air quality!). The issue is not about lack of technology or measures to increase the efficiency of nitrogen use in agriculture, improve livestock waste management, control emissions at end of pipe, or adopt fuels with lower content of sulfur or nitrogen. These technologies exist and are used in many places. The real challenge is to make governments aware and convince them that emissions from these, and other sources not related with the use of fossil fuels, are centrally important to air quality and should be part of any plan that attempts to deal effectively with air pollution, at a national and regional scale.