Rashid Shaikh

Particulate matter components, sources, and health: Systematic approaches to testing effects

Exposure to particulate matter (PM) is associated with adverse health outcomes. There has long been a question as to whether some components of the PM mixture are of greater public health concern than others so that the sources that emit the more toxic components could be controlled. In this paper, we describe the National Particle Component Toxicity (NPACT) initiative, a comprehensive research program that combined epidemiologic and toxicologic approaches to evaluate this critical question, partly relying on information from a national network of air quality monitors that provided data on speciated PM2.5 (PM with an aerodynamic diameter <2.5 μm) starting in 2000. We also consider the results of the NPACT program in the context of selected research on PM components and health in order to assess the current state of the field. Overall, the ambitious NPACT research program found associations of secondary sulfate and, to a somewhat lesser extent, traffic sources with health effects. Although this and other research has linked a variety of health effects to multiple groups of PM components and sources of PM, the collective evidence has not yet isolated factors or sources that would be closely and unequivocally more strongly related to specific health outcomes. If greater success is to be achieved in isolating the effects of pollutants from mobile and other major sources, either as individual components or as a mixture, more advanced approaches and additional measurements will be needed so that exposure at the individual or population level can be assessed more accurately. Enhanced understanding of exposure and health effects is needed before it can be concluded that regulations targeting specific sources or components of PM2.5 will protect public health more effectively than continuing to follow the current practices of targeting PM2.5 mass as a whole. Implications: This paper describes a comprehensive epidemiologic and toxicologic research program to evaluate whether some components and sources of PM may be more toxic than others. This question is important for regulatory agencies in setting air quality standards to protect people’s health. The results show that PM from coal and oil combustion and from traffic sources was associated with adverse health outcomes, but other components and sources could not definitively be ruled out. Thus, given current knowledge, the current practice of setting air quality standards for PM mass as a whole likely remains an effective approach to protecting public health.

First steps toward multipollutant science for air quality decisions.

Dominici et al have done an excellent job of laying out the rationale for moving toward a multipollutant scientific approach to address the health consequences of air pollution. They have, as well, provided some innovative statistical ideas in the hopes of accomplishing that. Few can challenge the logic of trying to address the range of pollutants which everyone is exposed, rather than tackling air pollutants one at a time. Given its logic, one might reasonably ask why has this not already happened? Many factors have contributed to the status quo, and it is useful to understand them as we take the first steps toward the next generation of multipollutant science and decision-making. We describe some of these factors below, and some concrete steps we and others are taking. The single-pollutant approach has been in place since the earliest versions of the U.S. Clean Air Act called for the establishment of National Ambient Air Quality Standards for so-called “criteria pollutants.” Although some clean-air actions have addressed multiple pollutants (eg, standards for motor vehicle emissions, which have addressed the emissions of several pollutants at the same time), the overriding impetus in the setting of these standards has been understanding the “independent” effects of individual pollutants so as to determine ambient levels that “protect public health with an adequate margin of safety” (CAA; 42 USC§7401). Among the reasons for this:

Airborne Fiber Levels During Asbestos Operations and Maintenance Work in a Large Office Building

Abstract While there is growing interest in the management of asbestos-containing materials (ACM) in buildings using operations and maintenance (O&M) programs, very little data are yet available on the effectiveness of such programs in reducing airborne fiber exposures of workers and other building occupants. This article presents and analyzes air sampling data collected in conjunction with O&M work over a 5-year period in a large Washington, DC, office building. ACM present in the building included pipe insulation, air handling unit insulation, acoustical ceiling plaster, and air supply ductwork. The database included 916 phase contrast microscopy (PCM) and 163 transmission electron microscopy (TEM) area samples. Seventy-six samples were analyzed by both methods. Overall, TEM and PCM concentrations averaged 0.0109 structures/ml (s/ml) for fibers longer than 5 μm (0.0035 s/ml after excluding two outliers) and 0.0059 fibers/ml, respectively. We examined fiber concentrations in several work activity categor...

Accountability Studies on Air Pollution and Health: the HEI Experience

Purpose of ReviewAssessing health effects of air quality interventions is of ever-increasing interest. Given the prominent role Health Effects Institute (HEI) has played in accountability research, this review focuses on HEI’s recent experiences, the challenges it has encountered, and provides possible directions for future research.Recent FindingsMost accountability studies to date have focused on effects of relatively short-term, local-scale, and sometimes temporary interventions. Only a few recent accountability studies have sought to investigate large-scale, multiyear regulatory programs. Common challenges encountered include lack of statistical power, how to account appropriately for background trends in air quality and health, and difficulties in direct attribution of changes in air pollution and health to a single intervention among many regulatory actions. New methods have been developed for accountability research that has shown promise addressing some of those challenges, including use of causal inference methods.SummaryThese and other approaches that would enhance the attribution of changes in air quality and health directly to an intervention should continue to be further explored. In addition, integration of social and behavioral sciences in accountability research is warranted, and climate related co-benefits and dis-benefits may be considered.

Airborne Fiber Levels in a Hospital Operations and Maintenance Program

Abstract Operations and maintenance (OM however, little information is available to evaluate the effectiveness of such programs. In this article we present data for airborne asbestos fiber concentrations for 394 samples (191 area and 203 personal) collected during 106 jobs that were part of an OM 90th, 0.2345 f/ml; 95th, 0.4176 f/ml; maximum: 0.8395 f/ml). The average for the area samples was 0.0196 f/ml (percentiles: 50th, 0.0096 f/ml; 90th, 0.0342 f/ml; 95th, 0.0542 f/ml; maximum: 0.4222...

Is the One-Hit Model of Carcinogenesis Conservative? Evidence from the National Toxicology Program’s Bioassay Databasea

Linear (one-hit) formulas of carcinogenesis are widely believed to be “conservative,” in the sense that they will rarely underestimate risks of cancer at low exposures. Such models are generally applied to the lifetime incidence of cancer at a specific site, with risks estimated from animal data at zero dose (control) and substantially higher doses that are appreciable fractions of the estimated maximum tolerated dose.