In Vitro Exposures in Diesel Exhaust Atmospheres: Resuspension of PM from Filters versus Direct Deposition of PM from Air

One of the most widely used <i>in vitro</i> particulate matter (PM) exposures methods is the collection of PM on filters, followed by resuspension in a liquid medium, with subsequent addition onto a cell culture. To avoid disruption of equilibria between gases and PM, we have developed a direct <i>in vitro</i> sampling and exposure method (DSEM) capable of PM-only exposures. We hypothesize that the separation of phases and post-treatment of filter-collected PM significantly modifies the toxicity of the PM compared to direct deposition, resulting in a distorted view of the potential PM health effects. Controlled test environments were created in a chamber that combined diesel exhaust with an urban-like mixture. The complex mixture was analyzed using both the DSEM and concurrently collected filter samples. The DSEM showed that PM from test atmospheres produced significant inflammatory response, while the resuspension exposures at the same exposure concentration did not. Increasing the concentration of resuspended PM sixteen times was required to yield measurable IL-8 expression. Chemical analysis of the resuspended PM indicated a total absence of carbonyl compounds compared to the test atmosphere during the direct-exposures. Therefore, collection and resuspension of PM into liquid modifies its toxicity and likely leads to underestimating toxicity

Polycyclic Aromatic Hydrocarbons in Fine Particulate Matter Emitted from Burning Kerosene, Liquid Petroleum Gas, and Wood Fuels in Household Cookstoves

This study measures polycyclic aromatic hydrocarbon (PAH) compositions in particulate matter emissions from residential cookstoves. A variety of fuel and cookstove combinations are investigated, including: (i) liquid petroleum gas (LPG), (ii) kerosene in a wick stove, (iii) wood (10 and 30% moisture content on a wet basis) in a forced-draft fan stove, and (iv) wood in a natural-draft rocket cookstove. The wood burning in the natural-draft stove had the highest PAH emissions followed by the wood combustion in the forced-draft stove and kerosene burning. LPG combustion has the highest thermal efficiency (∼57%) and the lowest PAH emissions per unit fuel energy, resulting in the lowest PAH emissions per useful energy delivered (in the unit of megajoule delivered, MJ_d). Compared with the wood combustion emissions, LPG burning also emits a lower fraction of higher molecular weight PAHs. In rural regions where LPG and kerosene are unavailable or unaffordable, the forced-draft fan stove is expected to be an alternative because its benzo­[<i>a</i>]­pyrene (B­[<i>a</i>]­P) emission factor (5.17–8.24 μg B­[<i>a</i>]­P/MJ_d) and emission rate (0.522–0.583 μg B­[<i>a</i>]­P/min) are similar to those of kerosene burning (5.36 μg B­[<i>a</i>]­P/MJ_d and 0.452 μg B­[<i>a</i>]­P/min). Relatively large PAH emission variability for LPG suggests a need for additional future tests to identify the major factors influencing these combustion emissions. These future tests should also account for different LPG fuel formulations and stove burner types

A Laboratory Comparison of Emission Factors, Number Size Distributions, and Morphology of Ultrafine Particles from 11 Different Household Cookstove-Fuel Systems

Ultrafine particle (UFP) emissions and particle number size distributions (PNSD) are critical in the evaluation of air pollution impacts; however, data on UFP number emissions from cookstoves, which are a major source of many pollutants, are limited. In this study, 11 fuel-stove combinations covering a variety of fuels and different stoves are investigated for UFP emissions and PNSD. The combustion of LPG and alcohol (∼10¹¹ particles per useful energy delivered, particles/MJ_d), and kerosene (∼10¹³ particles/MJ_d), produced emissions that were lower by 2–3 orders of magnitude than solid fuels (10¹⁴–10¹⁵ particles/MJ_d). Three different PNSD typesunimodal distributions with peaks ∼30–40 nm, unimodal distributions with peaks <30 nm, and bimodal distributionswere observed as the result of both fuel and stove effects. The fractions of particles smaller than 30 nm (<i>F</i>₃₀) varied among the tested systems, ranging from 13% to 88%. The burning of LPG and alcohol had the lowest PM_2.5 mass emissions, UFP number emissions, and <i>F</i>₃₀ (13–21% for LPG and 35–41% for alcohol). Emissions of PM_2.5 and UFP from kerosene were also low compared with solid fuel burning but had a relatively high <i>F</i>₃₀ value of approximately 73–80%