A new study has found that global estimates of black carbon emissions in certain areas of India and China could be two to three more times concentrated than previously thought. Black carbon, a major element of soot, is a particle that is generated by the incomplete combustion of fossil fuels, biofuel or biomass.
Published in Proceedings of the National Academy of Sciences, a team of researchers from France and China developed a new model for discerning the amount of black carbon pollution in the air. Previous models had failed to take into account regional differences, and instead provided information at the country level. By mapping regions rather than countries, the study indicated that parts of India and China could have as much as 130 percent higher black carbon concentrations than shown in standard country models.
Short-term and long-term exposure to black carbon can lead to a broad range of health impacts, including respiratory and cardiovascular effects as well as cancer and premature death, according to the U.S. Environmental Protection Agency. Black carbon contributes to particulate matter, or PM, pollution, which is made up of a mixture of solid particles and liquid droplets in the air. Black carbon falls within the PM2.5 category, otherwise known as “fine particles,” with diameters that are between 1.0 and 2.5 micrometers and are considered to pose the greatest health risks.
A recent World Health Organization study, “2010 Global Burden of Disease,” found that outdoor air pollution is contributing annually to over 3.2 million premature deaths worldwide — including 1.2 million in East Asia and 712,000 in South Asia in 2010.
In China the impacts of air pollution received major media attention in 2013, as the problem seemed to spiral out of control in certain urban areas — leading to highly limited visibility, increased health impacts and sustained public outcry. The Chinese government has been recently making very public efforts to reduce air pollution.
However an article in Monday’s New York Times pointed out that while Beijing may be sending out warnings, the situation in Indian cities like Delhi would seem to be even worse. “The United States Embassy in Beijing sent out warnings in mid-January, when a measure of harmful fine particulate matter known as PM2.5 went above 500, in the upper reaches of the measurement scale, for the first time this year:”
“But for the first three weeks of this year, New Delhi’s average daily peak reading of fine particulate matter from Punjabi Bagh, a monitor whose readings are often below those of other city and independent monitors, was 473, more than twice as high as the average of 227 in Beijing. By the time pollution breached 500 in Beijing for the first time on the night of Jan. 15, Delhi had already had eight such days. Indeed, only once in three weeks did New Delhi’s daily peak value of fine particles fall below 300, a level more than 12 times the exposure limit recommended by the World Health Organization.“
Further analysis suggested that this discrepancy in coverage is partially to blame on China’s secrecy around the issue as well as the fact that the United States Embassy in Beijing had helped raise awareness in China by posting air quality readings on Twitter.
“I think when you have the sense that they’re hiding something, it galvanizes public attention in a counterintuitive way,” Ananth Krishnan, the China correspondent for The Hindu, told the New York Times about China. “Coverage of air quality by the Indian news media will have to change very soon,” he added, saying that India has never approached the populist demand to improve air quality that China is experiencing now.
While the issue of black carbon is an immediate concern for those living in urban India and China, it is also a global priority when it comes to climate change. Black carbon is a short-lived climate forcer, now believed to be the second-leading contributor to global warming behind carbon dioxide and ahead of methane. Short-lived climate forcers have a much shorter atmospheric lifetime than carbon, but are also more intense trappers of heat. Black carbon stays in the atmosphere for days or weeks, but is 680 times more effective at trapping heat than carbon dioxide. Not only does black carbon directly absorb sunlight, but it darkens the surface of snow or ice, which is contributing to snowpack and glacier melt in mountain ranges around the world as well as the Arctic.
Black carbon emissions come primarily from biomass burning, such as forest fires and deforestation, diesel engines, and residential cooking and heating.
Cutting emissions of black carbon would be felt almost immediately in terms of both public health and climate benefits, unlike with carbon dioxide which takes decades to leave the atmosphere. However it is not such a straightforward process, as black carbon has various effects on the atmosphere and soot — some of which help warm the atmosphere and some that actually cool it. It appears cutting diesel emissions is the most practical approach to quickly reducing black carbon. For a detailed analysis of these interactions, see this Yale360 article, “Black Carbon and Warming.”
As if to reiterate the connection between local and global issues when it comes to air pollution and climate change, a recent study found that the West Coast of the U.S. is receiving significant amounts of air pollution from China. And where are these pollutants coming from — the study found that 17 percent of black carbon associated with Chinese emissions were linked to producing goods for export. The U.S. is China’s second-largest trading partner. China is the world’s largest greenhouse gas emitter, but U.S. demand for products is contributing to China’s local air pollution problems.