Black carbon as an additional indicator of the adverse health effects of airborne particles compared with PM10 and PM2.5

Abstract

Background: Current air quality standards for particulate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM(10)) or ≤ 2.5 μm (PM(2.5))] as a metric. It has been suggested that particles from combustion sources are more relevant to human health than are particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration.

Objectives: We evaluated the value of black carbon particles (BCP) as an additional indicator in air quality management.

Methods: We performed a systematic review and meta-analysis of health effects of BCP compared with PM mass based on data from time-series studies and cohort studies that measured both exposures. We compared the potential health benefits of a hypothetical traffic abatement measure, using near-roadway concentration increments of BCP and PM(2.5) based on data from prior studies.

Results: Estimated health effects of a 1-μg/m3 increase in exposure were greater for BCP than for PM(10) or PM(2.5), but estimated effects of an interquartile range increase were similar. Two-pollutant models in time-series studies suggested that the effect of BCP was more robust than the effect of PM mass. The estimated increase in life expectancy associated with a hypothetical traffic abatement measure was four to nine times higher when expressed in BCP compared with an equivalent change in PM(2.5) mass.

Conclusion: BCP is a valuable additional air quality indicator to evaluate the health risks of air quality dominated by primary combustion particles.

Figure 1

Single-city, single-pollutant estimates for PM₁₀ and BS and all-cause mortality. Year indicates year of publication. References: Amsterdam, 1996 [Verhoeff et al. (1996)]; Amsterdam, 2001 [Roemer and van Wijnen (2001a)]; Athens, Barcelona, Birmingham, Cracow, London, and Paris, 2001 [Katsouyanni et al. (2001)]; Le Havre, Paris, and Rouen, 2001 [Zeghnoun et al. (2001)]; London, 1999 [Bremner et al. (1999)]; the Netherlands, 2000 [Hoek et al. (2000)]; West Midlands, 2001 [Anderson et al. (2001)]. ^aCities included in the pooled estimate. ^bZeghnoun et al. (2001). ^cKatsouyanni et al. (2001).

Figure 2

Study-specific street:background ratios for PM mass and BCP concentrations. Blue, ≥ 24-hr average along highways; green, ≥ 24-hr average along inner-city roads; red, daytime and ≤ 12-hr measurements (all inner-city roads). Data from Boogaard et al. (2011), Cyrys et al. (2003), Fischer et al. (2000), Fromme et al. (2005), Funasaka et al. (2000), Harrison et al. (2004), Janssen et al. (1997, 2001, 2008), Kinney et al. (2000), Lena et al. (2002), Riediker et al. (2003), Roemer and van Wijnen (2001b), Roorda-Knape et al. (1998), Roosli et al. (2001), and Smargiassi et al. (2005).