Pulmonary inflammatory effects of source-oriented particulate matter from California's San Joaquin Valley

Abstract

The EPA regulates ambient particulate matter (PM) because substantial associations have been established between PM and health impacts. Presently, regulatory compliance involves broad control of PM emission sources based on mass concentration rather than chemical composition, although PM toxicity is likely to vary depending upon PM physicochemical properties. The overall objective of this study was to help inform source-specific PM emission control regulations. For the first time, source-oriented PM was collected from the atmosphere in Fresno, CA, onto 38 source/size substrates. Mice were exposed via oropharyngeal aspiration to equivalent mass doses [50 μg] of two size fractions: ultrafine (Dp < 0.17μm) and submicron fine (0.17 < Dp < 1 μm) during summer and winter seasons. At 24 hours post-exposure, cellular and biochemical indicators of pulmonary inflammation were evaluated in the bronchoalveolar lavage fluid. Significant inflammatory responses were elicited by vehicle, regional background, and cooking PM sources that were dependent on season and particle size. This is the first study of source-oriented toxicity of atmospheric PM and supports source-specific emissions control strategies.

Differential pulmonary effects of wintertime California and China particulate matter in healthy young mice

“…Because of the growing evidence that particle chemical composition plays an important role in eliciting health effects (Dreher 2000; Plummer et al 2015; Valavanidis et al 2008), the chemical composition of both PM samples was determined. Atmospheric PM is very complex, comprising a large number of compounds including organics, inorganic species, elemental carbon, crustal components, and metals.…”

“…Such is the case here where the Sacramento PM had higher levels of oxidized organic compounds compared with the Taiyuan PM. Previous studies indicate that oxidized organic compounds in fine PM are strongly linked with inflammatory responses (Happo et al 2010; Plummer et al 2015). Thus, it could be that the higher levels of oxidized organic compounds in the Sacramento PM are responsible for its ability to generate a greater acute inflammatory response in the lungs.…”

“…The mice were maintained for one week prior to the beginning of the experiment to allow for acclimation and then randomly assigned to three exposure groups (n=10/ group) by random number generation: 1) vehicle control (Milli-Q water), 2) Taiyuan PM, and 3) Sacramento PM. Fifty microliters of Milli-Q water, Taiyuan PM (1 µg/µL) or Sacramento PM (1 µg/µL) was delivered to the lungs of mice via oropharyngeal aspiration after mice were anesthetized via inhalation of isoflurane with oxygen (3:1 ratio) (Gilmour et al 2007; Plummer et al 2015). For each exposure group, six animals were used to collect BALF and, while four animals were used for histological assessment only.…”

Retrospective source attribution for source-oriented sampling

“…One of the more important conclusions of this work is further validation of the source-oriented sampling technique. In companion work (Plummer et al, 2015), the differential toxicity of each source was investigated using various pulmonary endpoints, showing that (a) different sources do, in fact, elicit significantly different toxicological responses, (b) similar sources are more or less toxic depending on season and size, (c) different sources are toxic in different ways and (d) some sources elicit no toxicity above control. In combination, these results corroborate the feasibility and rationale of a paradigm shift from current regulatory practices of treating all emissions equally to a source-or risk-based regulatory strategy.…”

“…In total, we posit that CV1 captured dinnertime cooking emissions, largely charcoal-and wood-fired outdoor barbequing, from residential sources to the north of the site while CV7 predominantly captured commercial dinnertime cooking emissions from sources to the west of the site. As shown in companion work (Plummer et al, 2015), this turns out to be an important distinction since the toxicity of these two sources is quite different. The percent composition of the wintertime version of CV1 on a particle class basis is 36.8% K/EC/OC, 25.2% K/CAN, 16.2% CAN, 9.4% EC/OC, 6.8% EC and 5.5% K, making this CV clearly attributable to local sources of biomass combustion.…”