Black carbon linked to increased cardiovascular risk; exacerbated by co-exposure to motor vehicle emissions
Black carbon (BC) from incomplete biomass and fossil fuel combustion is the most strongly light-absorbing component of particulate matter (PM) air pollution and a major climate-forcing emission. A new international study led by McGill University (Canada) Professor Jill Baumgartner suggests that black carbon may also increase the risk of cardiovascular disease. The team’s findings are published in the Proceedings of the National Academy of Sciences of the United States (PNAS).
China’s particulate matter (PM) air pollution significantly exceeds health guidelines and is driven by industrial emissions, motor vehicles, and household use of biomass and coal fuels. Baumgartner and her colleagues measured the daily exposure to different types of air pollutants, including black carbon, in 280 women (mean age 51.9 y) in China’s rural Yunnan province, where biomass fuels are commonly used. They found that found that BC exposure from biomass smoke is more strongly associated with blood pressure—which directly impacts cardiovascular risk—than total PM mass, and that co-exposure to motor vehicle emissions may strengthen BC’s impact. Air pollution mitigation efforts focusing on reducing combustion pollution are likely to have major benefits for climate and human health.
China’s unprecedented economic growth is fueling massive increases in industrial and motor vehicle pollution, and 700 million Chinese homes still cook with wood and coal fuels. The Chinese government is setting new targets to improve its air quality. We wanted to identify the pollution sources that most impact human health to help inform these pollution control efforts.—Jill Baumgartner
The researchers outfitted women with wearable air samplers that collected fine particulate matter.The particulate samples were then analyzed for different pollutant types, including black carbon. The women’s blood pressure, salt intake, physical activity, body mass index, and their proximity to highways were also measured.
We found that exposure to black carbon pollutants had the largest impact on women’s blood pressure, which directly impacts cardiovascular risk. In fact, black carbon’s effect was twice that of particulate matter, the pollutant measured most often in health studies or evaluating cleaner cookstoves. Black carbon from wood burning is considered very important for climate warming. Our research shows that it may also be an important pollutant for health.—Jill Baumgartner
In addition, the researchers found that women living closer to highways and exposed to both wood smoke and traffic emissions had three times higher blood pressure than women who lived away from highways.
BC had the strongest association with systolic blood pressure (SBP) (4.3 mmHg; P < 0.001), followed by PM mass and water-soluble organic mass. The team also found that effect of BC on SBP was almost three times greater in women living near the highway [6.2 mmHg; 95% confidence interval (CI), 3.6 to 8.9 vs. 2.6 mmHg; 95% CI, 0.1 to 5.2].
Our findings suggest that BC has direct relevance as an important environmental risk factor for cardiovascular diseases and support the use of BC as a pollution indicator in future health studies and in the evaluation of air pollution mitigation programs. More broadly, our results may be useful in forming policy aimed at reducing air pollution and improving public health in China and other developing countries.
China recently committed to spending US$275 billion over the next 5 y to reduce air pollution, but targets for new vehicle emission standards are absent from recently announced mitigation plans. In addition, China’s current air pollution targets and programs focus on PM reductions. The BC reduction achieved with any mitigation strategy is not always proportional to the reduction in PM mass, and our results show that BC may be more strongly associated with health outcomes in addition to warming the climate. As motorized transport and subsequent traffic emissions increase throughout China, air pollution policies and mitigation efforts that focus on BC control might have the largest benefits for climate and human health.—Baumgartner et al.
Jill Baumgartner, Yuanxun Zhang, James J. Schauer, Wei Huang, Yuqin Wang, and Majid Ezzati (2014) “Highway proximity and black carbon from cookstoves as a risk factor for higher blood pressure in rural China” PNAS doi: 10.1073/pnas.1317176111