Public health and components of particulate matter: The changing assessment of black carbon

Abstract

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM_2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments.

In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries.

Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM_2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models.

Natural “interventions” - reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems – demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g., carbonaceous species, may cause harm, aiding interpretation of epidemiological studies.

Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer, and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the U.S. EPA rubric for judging possible causality of PM_2.5. mass concentrations, be used to assess which PM_2.5. species are most harmful to public health.

Implications: Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM_2.5 species in models; using better measurements of subject exposure) have also occurred. “Natural intervention” studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM_2.5 species is suggested.

A list of acronyms will be found at the end of the article.

Disclaimer and Acknowledgment

The views expressed herein represent those of the authors alone, and do not purport to represent views of any U.S. government agency. The authors thank Dr. David Streets (Argonne National Laboratory), Dr. George Hidy, Ralph Freedman (U.S. Department of Energy), and JoAnn Yuill and Diana Hendershot (National Energy Technology Laboratory) for invaluable assistance.

Additional information

Notes on contributors

Thomas J. Grahame

Thomas J. Grahame has worked on economic and environmental issues related to energy and electricity for the past 37 years, including the past 35 at the U.S. Department of Energy (DOE). Prior to his DOE work, he analyzed energy issues for U.S. Senator John Durkin (D, NH), serving on the U.S. Senate Energy and Natural Resources Committee, where much of his time was involved with the Public Utility Regulatory Policies Act (PURPA), a law that began to open the door to competition in electricity generation in the early 1980s. Mr. Grahame has an undergraduate degree in Government, and a Master’s Degree in City and Regional Planning, both from Harvard University.

Mr. Grahame has authored or co-authored seven journal articles on the health impacts of different air pollutants (e.g., sulfate or black carbon); analyzing toxicological and epidemiological evidence with regard to which types of particulate matter appear to be most harmful; exploring whether study methodologies consistently cause studies to come to different conclusions; analyzing toxicological, human panel, and population-based epidemiological studies, concluding that black carbon emissions were likely causally related to eight different cardiovascular mortality or morbidity health effects; and the hypothesis that vehicular emissions marked by black carbon may cause people to die prematurely because these emissions cause oxidative stress, thus causing premature erosion of protective telomeres and quicker biological aging.

Mr. Grahame has also analyzed underlying studies and authored DOE comments to the U.S. Environmental Protection Agency (EPA) regarding the National Ambient Air Quality Standards for Particulate Matter, in 1995 and from 2002 through 2009. He initiated the most comprehensive federal government study of externalities (the field of attempting to value harm or benefit from pollution in economic terms, and then incorporate subsequently determined economic values in prices paid for relevant good and services) in 1990; authored DOE testimony on externalities before Massachusetts and Texas regulators; and defended DOE testimony in Massachusetts. Additionally, Mr. Grahame was the author of the 140-page annex on transmission access issues, part of the National Energy Strategy of the early 1990s, which led to the Energy Policy Act of 1992.

Rebecca Klemm

Richard B. Schlesinger, Ph.D., is Associate Dean for Academic Affairs and Research in the Dyson College of Arts and Sciences of Pace University, New York, NY, and Professor of Biology and Environmental Science. He received his B.A. degree in Biology from Queens College of the City University of NY, and his M.S. and Ph.D. degrees in Biology/Environmental Health Science, from New York University. Prior to his appointment at Pace University, he was Professor of Environmental Medicine and Director of the Systemic Toxicology Program in the Department of Environmental Medicine, NYU School of Medicine, as well as Director of the Graduate Program in Environmental Health Science at the NYU Graduate School of Arts and Sciences. He has developed and taught various courses at the graduate and undergraduate level in the areas of general toxicology, systemic toxicology, pulmonary toxicology, environmental health, and industrial hygiene at New York University.

Dr. Schlesinger has published extensively in the areas of respiratory toxicology of ambient air pollutants, especially related to the deposition of inhaled particles and the relationship of both particulate and gaseous air pollutant exposure to the pathogenesis of non-neoplastic pulmonary disease, and most recently in relation to overall morbidity and mortality. He is recipient of the Society of Toxicology Inhalation Specialty Section Career Achievement Award, the ILSI Morgareidge Award for Achievement in Inhalation Toxicology, and the Herbert Stokinger Award for contributions to the field of industrial and environmental toxicology. He is a Fellow of the Academy of Toxicological Sciences.

Dr. Schlesinger has served on numerous National Academy of Science committees, including the Committee on Research Priorities for Airborne Particulate Matter, the Committee on Gulf War and Health III, and the Committee on Acute Exposure Guideline Levels. He served as a member of the AIHA ERPG Committee. He has served as consultant to various governmental agencies, contributing to U.S. Environmental Protection Agency (EPA) Air Pollutant Criteria Documents and Integrated Science Assessments, and to WHO, contributing to the Clean Air for Europe Group air quality documents. He has served as a member of the EPA Clean Air Scientific Advisory Committee Review Panel for Sulfur Oxides and is currently a member of this Committee for Nitrogen Oxides. He is also a Science Advisor to the New York State Energy Research and Development Agency, and an Associate Editor of the journal, Inhalation Toxicology.

Richard B. Schlesinger

Rebecca Klemm, Ph.D., is president of Klemm Analysis Group, and directs her company’s projects to ensure the timely completion of every project within the budget allocated and adherence to strict quality control standards. Dr. Klemm has directed many projects in the area of health services research for the U.S. Departments of Veterans Affairs and of Health and Human Services, and commercial clients. She has also published extensively on the effects of air pollution on human health. Dr. Klemm has also specialized in analyses regarding public policy and regulation within a legal environment for the past 20 years. The range of projects for which she has served as an expert includes policy and regulation, employment (including Title VII, ADEA, and pay equity), Section 482 tax, quality control, product liability, and statistical auditing. She has combined her statistical expertise with her training in operations research and stochastic programming to a variety of subject matters, including the performance of econometric modeling for the U.S. Department of Energy.

Dr. Klemm served as Principal Investigator of the Coordinating Center for a large multi-center translational study of diabetes in managed care organizations for the Centers for Disease Control and Prevention (CDC). She has served as Technical Director of a contract to provide statistical, epidemiologic, and data management services to CDC for several years. Dr. Klemm has served two terms as one of the seven scientists of the National Conference of Lawyers and Scientists of the American Association for the Advancement of Science and the Science and Technology Section, American Bar Association.