Coverage of Kaufman Study

Professor Joel Kaufman received wide coverage for a study his research team published in the Feb. 1 edition of the New England Journal of Medicine on the association between fine particulate air pollution and cardiovascular disease and death among postmenopausal women.

Stories were carried by all three major television networks, National Public Radio, the Wall Street Journal, US News and World Report, and as far away as England, Australia, China, and India. It was also the top story on the National Institutes of Health’s (NIH) Research Matters column.

The study found that the magnitude of health effects may be larger than previously recognized, which could provide impetus for policy change.

The study, led by Epidemiology doctoral student Kristin Miller, evaluated long-term exposure to air pollution and the incidence of cardiovascular disease in the Women’s Health Initiative, a large prospective cohort study. Unlike prior research, the study examined not only differences between cities, but also between communities within a city. Study results linked a woman’s first cardiovascular event, such as coronary heart disease, heart attack, or stroke, with the smallest particulate air pollution—particles of less than 2.5 microns in diameter and invisible to the human eye (PM_2.5).

The team studied healthy women who lived in 36 US cities, following them for an average of six years, using medical records to confirm each cardiovascular disease event. Each woman’s exposure was determined by a network of 573 air pollution monitors (most lived within six miles of a monitor). These monitors showed the highest air pollution in Riverside, California, and the lowest in Honolulu.

Particulate air pollution in some urban neighborhoods puts women at increased risk of cardiovascular disease. © www.photo.com

Of the 65,893 women studied, 1816 had one or more cardiovascular events during the study. Each increase of 10 micrograms per cubic meter of fine particulate air pollution was associated with a 24% increase in the risk of heart disease or stroke and a 76% rise in the risk of death.

The researchers found that effects between neighborhoods within a city were often larger than those between cities. They also found that the association between the PM2.5 level and cardiovascular disease was stronger with increasing obesity.

The mechanism by which fine particulate air pollution increases the risk of cardiovascular disease is still unknown, although Kaufman’s ongoing MESA Air Pollution study, as well as studies in his diesel exhaust exposure facility, are seeking answers.

The study was funded by the Environmental Protection Agency, through Professor Jane Koenig’s Northwest Center for Particulate Air Pollution and Health, and the National Institute of Environmental Health Sciences. The Women’s Health Initiative is funded by the National Heart, Lung, and Blood Institute.

Further Reading

Miller KA, Siscovick DS, Sheppard L, Shepherd K, Sullivan JH, Anderson GL, Kaufman JD. Longterm exposure to air pollution and incidence of cardiovascular events in women. N Engl J Med 2007 Feb 1;356(5):447-458.

Tracking Individual Exposure

While ambient air monitors can estimate our exposure to air pollution, they can’t tell exactly what we breathed or how our body reacted to it. Assistant Professor Christopher Simpson is developing biomarkers that can help identify the exact components of our exposure. Examples of exposure biomarkers developed in Simpson’s lab include metabolites of diesel exhaust, wood smoke, and organophosphate pesticides in biological specimens (generally urine or blood samples).

Chris Simpson in his lab. Photo by Jennifer Gill.

One project traces methoxyphenols, which are produced when the wood polymer lignin is burned. Lignin is specific to wood, so these markers couldn’t be confused with compounds from, for example, vehicle exhaust.

Using departmental volunteers, he conducted controlled human exposures to wood smoke, in order to study the dose response and time course of urinary excretion of these compounds. He is now using these urinary methoxyphenols to estimate personal exposure to biomass smoke in occupationally exposed firefighters, and in rural communities in the developing world that use biomass fuels for cooking and heating.

Simpson also uses molecular markers to measure and identify the different components of particulate matter air pollution. Because different sources of air pollution display different types of toxicity in humans, it is important to apportion exposure to air pollution among the different sources, he said.

The Simpson lab is developing new analytical methods to identify and quantify novel marker compounds in air particulate matter, and is evaluating how these markers perform as variables in computer models.

With research scientist/graduate student Mike Paulsen, Simpson is studying biomarkers of exposure to diesel exhaust. Diesel exhaust contains numerous known and suspected cancer-causing components including polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs. Epidemiological studies suggest links between diesel exhaust and lung cancer, asthma, and other diseases. However, a major limiting factor in studying the connection between diesel exhaust and disease is the lack of accurate exposure measures, Simpson said. Effective biomarkers will provide researchers with tools to study health effects of exposure to diesel exhaust and to evaluate changes to exposures resulting from environmental protection efforts or workplace exposure control mechanisms.

The Simpson lab, in collaboration with Japanese colleagues Akira Toriba and Kazuichi Hayakawa, is trying to measure diesel exposures by measuring levels of urinary metabolites of diesel-specific types of PAH.

Paulsen’s thesis research focuses on 1-Nitropyrene (1-NP), which is also being used as an atmospheric marker because it is formed almost exclusively in diesel engines.

Paulsen and Toriba are developing highly sensitive assays for 1-NP urinary metabolites by using gas chromatography and high performance liquid chromatography coupled with mass spectrometry. The assays require complex sample preparation and optimal performance of analytical instrumentation to measure metabolites at part-per-quadrillion levels in urine. Based on preliminary results, this level of sensitivity appears sufficient to detect several of the 1-NP metabolites from individuals exposed to ambient levels of diesel exhaust. Paulsen and colleagues plan to test the method further on air and urine samples from bus and taxi drivers in Peru and China.

Chris Simpson's Bibliography.