Intake fraction of nonreactive vehicle emissions in US urban areas

Abstract

Intake fraction, which is the fraction of emissions that are inhaled by people, quantifies the ''exposure efficiency'' of an emission source. We use three methods to estimate intake fractions for vehicle emissions in US urban areas. First, we use a one-compartment steady-state mass-balance model, incorporating meteorological and demographic data. Second, we use an empirical emissions-to-concentration relationship for vehicle carbon monoxide developed for 15 US urban areas. Third, we analyze model results for benzene and diesel particulate matter from the US Environmental Protection Agency's National-scale Air Toxics Assessment (NATA). The population-weighted mean intraurban intake fraction for nonreactive gaseous vehicle emissions in US urban areas is estimated to be in the range 7-21 per million, with a best estimate of 14 per million. The intake fraction for diesel particles is 4 per million, based on NATA results. An intake fraction of 4 per million means that 4 mg of pollution are inhaled per kg emitted. Intake fraction values for urban vehicle emissions are usually higher in winter than in summer because of seasonal variability in the atmospheric mixing height. The results presented in this work can be used in health risk assessments, cost-benefit analyses, and other investigations that require a summary of the emission-to-intake relationship. r

Evaluation of intake fractions for different subpopulations due to primary fine particulate matter (PM2.5) emitted from domestic wood combustion and traffic in Finland

“…The other studies published in US have reported iF values 1.2-9.4 per million (Greco et al 2007;Marshall et al 2005;Evans et al 2002;Levy et al 2002a). In NATA (National-scale Air Toxic Assessment) study, Marshall et al (2005) reported population-weighted iF mean value of 4.4 per million for urban on-road traffic based diesel PM 2.5 emission sources among US urban counties.…”

Modeling residential exposure to secondhand tobacco smoke

“…In contrast, the 24-h average exposure concentration of House #2 occupants varied from 24 to about 60 µg m −3 and their intake fraction varied from 1000 to 2600 ppm, when going from "avoider" to "follower" behavior (Table 2). Notably, these individual intake fractions are much larger than estimates of population intake fraction for pollutant releases to outdoor air from motor vehicles in US urban areas (Marshall et al, 2005) or power plants (Levy et al, 2003), which average approximately 14 ppm and 1 ppm, respectively. The results obtained for SHS here compare favorably to the limited intake fraction information published for indoor releases.…”

Evaluating the application of multipollutant exposure metrics in air pollution health studies

“…Measurement methods have included tracer gas experiments where chemical compounds are purposely released and measured to act as a fingerprint for a particular source (Marshall and Nazaroff, 2007). Modeling methods range from simple, onecompartment models that combine meteorological (e.g., wind speed and mixing height), demographic, and land area data (Marshall et al, 2005) to complex dispersion models (Greco et al, 2007;Levy et al, 2003).…”

“…Intake fractions also use emission information, and have primarily been used as an indicator of exposure to a specific source. Intake fractions have been used for primary (Lobscheid et al, 2012;Marshall et al, 2005) and secondary pollutants (Greco et al, 2007;Levy et al, 2003); inhalation and other intake pathways such as ingestion (Bennett et al, 2002a); and for varied sources such as motor vehicles (Marshall et al, 2006), power plants (Levy et al, 2003), and dry cleaners (Evans et al, 2000).…”