13 research outputs found
PM biological effect modification by gases in urban air
In its most-recent document summarizing the state of the science related to PM, the National Research Council (NRC) stated that "a finding that the effect of particles depends on the concentration of another pollutant--that is, 'effect modification'--would have implications for setting NAAQS independently for the various criteria pollutants". This dissertation contains a series of manuscripts describing new methods and approaches to evaluate the dynamic entanglements of the composition and toxic effects of gases and particles described by the NRC. The first study develops a new in vitro exposure method that is able to expose cultured human lung cells to the particulate matter (PM) present in air pollution mixtures while they are still in equilibrium with the gases surrounding them. When coupled with a gas-only in vitro exposure method already in use, and the analytical equipment in our laboratory, we have a uniquely suited set of tools to investigate 'entanglement' phenomena. The remaining three manuscripts describe a three-part study designed to demonstrate dynamic entanglements among gaseous organic compounds (VOCs), PM, and their subsequent biological effects. We studied these entanglements in increasingly complex VOC and PM mixtures in urban-like conditions in a large outdoor chamber. First, we demonstrate the existence of 'effect modification' for the case of single gas-phase toxicants and an inherently non-toxic PM (mineral oil aerosol, MOA). In the presence of the single gas-phase toxicant in the dark, the initially non-toxic PM became toxic to lung cells in the PM-only in vitro exposure system. Next, we used sunlight to create secondary gas-phase toxicants from a complex mixture of 54 VOCs similar to those in urban air, with the MOA used in part one. Finally, testing was further applied to systems with primary diesel exhaust (gas and PM) from a single vehicle operated with different types of fuel. In almost every case, we observed increases in cellular toxicity when chamber contents were photochemically aged. These studies prove unambiguously that the toxicity inherent to one phase of an air pollution mixture can affect the toxicity of another - precisely the 'effect modification' described by the NRC
A Toxicogenomic Comparison of Primary and Photochemically Altered Air Pollutant Mixtures
Background: Air pollution contributes significantly to global increases in mortality, particularly within urban environments. Limited knowledge exists on the mechanisms underlying health effects resulting from exposure to pollutant mixtures similar to those occurring in ambient air. In order to clarify the mechanisms underlying exposure effects, toxicogenomic analyses are used to evaluate genomewide transcript responses and map these responses to molecular networks
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 in vitro 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 in vitro 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
The Gillings Sampler – An electrostatic air sampler as an alternative method for aerosol in vitro exposure studies
There is growing interest in studying the toxicity and health risk of exposure to multi-pollutant mixtures found in ambient air, and the U.S. Environmental Protection Agency (EPA) is moving towards setting standards for these types of mixtures. Additionally, the Health Effects Institute's strategic plan aims to develop and apply next-generation multi-pollutant approaches to understanding the health effects of air pollutants. There's increasing concern that conventional in vitro exposure methods are not adequate to meet EPA's strategic plan to demonstrate a direct link between air pollution and health effects. To meet the demand for new in vitro technology that better represents direct air-to-cell inhalation exposures, a new system that exposes cells at the air-liquid interface was developed. This new system, named the Gillings Sampler, is a modified two-stage electrostatic precipitator that provides a viable environment for cultured cells. Polystyrene latex spheres were used to determine deposition efficiencies (38-45%), while microscopy and imaging techniques were used to confirm uniform particle deposition. Negative control A549 cell exposures indicated the sampler can be operated for up to 4 hours without inducing any significant toxic effects on cells, as measured by lactate dehydrogenase (LDH) and interleukin-8 (IL-8). A novel positive aerosol control exposure method, consisting of a p-tolualdehyde (TOLALD) impregnated mineral oil aerosol (MOA), was developed to test this system. Exposures to the toxic MOA at a 1 ng/cm2 dose of TOLALD yielded a reproducible 1.4 and 2 fold increase in LDH and IL-8 mRNA levels over controls. This new system is intended to be used as an alternative research tool for aerosol in vitro exposure studies. While further testing and optimization is still required to produce a “commercially ready” system, it serves as a stepping-stone in the development of cost-effective in vitro technology that can be made accessible to researchers in the near future
Mutagenicity and Pollutant Emission Factors of Solid-Fuel Cookstoves: Comparison with Other Combustion Sources
BACKGROUND: Emissions from solid fuels used for cooking cause ~4 million premature deaths per year. Advanced solid-fuel cookstoves are a potential solution, but they should be assessed by appropriate performance indicators, including biological effects.
OBJECTIVE: We evaluated two categories of solid-fuel cookstoves for eight pollutant and four mutagenicity emission factors, correlated the mutagenicity emission factors, and compared them to those of other combustion emissions.
METHODS: We burned red oak in a 3-stone fire (TSF), a natural-draft stove (NDS), and a forced-draft stove (FDS), and we combusted propane as a liquified petroleum gas control fuel. We determined emission factors based on useful energy (megajoules delivered, MJd) for carbon monoxide, nitrogen oxides (NOx), black carbon, methane, total hydrocarbons, 32 polycyclic aromatic hydrocarbons, PM2.5, levoglucosan (a wood-smoke marker), and mutagenicity in Salmonella.
RESULTS: With the exception of NOx, the emission factors per MJd were highly correlated (r ≥ 0.97); the correlation for NOx with the other emission factors was 0.58-0.76. Excluding NOx, the NDS and FDS reduced the emission factors an average of 68 and 92%, respectively, relative to the TSF. Nevertheless, the mutagenicity emission factor based on fuel energy used (MJthermal) for the most efficient stove (FDS) was between those of a large diesel bus engine and a small diesel generator.
CONCLUSIONS: Both mutagenicity and pollutant emission factors may be informative for characterizing cookstove performance. However, mutagenicity emission factors may be especially useful for characterizing potential health effects and should be evaluated in relation to health outcomes in future research. An FDS operated as intended by the manufacturer is safer than a TSF, but without adequate ventilation, it will still result in poor indoor air quality.
CITATION: Mutlu E, Warren SH, Ebersviller SM, Kooter IM, Schmid JE, Dye JA, Linak WP, Gilmour MI, Jetter JJ, Higuchi M, DeMarini DM. 2016. Mutagenicity and pollutant emission factors of solid-fuel cookstoves: comparison with other combustion sources. Environ Health Perspect 124:974-982; http://dx.doi.org/10.1289/ehp.1509852
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<sub>d</sub>). 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<sub>d</sub>) 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<sub>d</sub> 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 (∼10<sup>11</sup> particles per useful energy delivered, particles/MJ<sub>d</sub>), and kerosene (∼10<sup>13</sup> particles/MJ<sub>d</sub>), produced emissions that were lower by 2–3 orders
of magnitude than solid fuels (10<sup>14</sup>–10<sup>15</sup> particles/MJ<sub>d</sub>). Three different PNSD typesunimodal
distributions with peaks ∼30–40 nm, unimodal distributions
with peaks <30 nm, and bimodal distributionswere observed
as the result of both fuel and stove effects. The fractions of particles
smaller than 30 nm (<i>F</i><sub>30</sub>) varied among
the tested systems, ranging from 13% to 88%. The burning of LPG and
alcohol had the lowest PM<sub>2.5</sub> mass emissions, UFP number
emissions, and <i>F</i><sub>30</sub> (13–21% for
LPG and 35–41% for alcohol). Emissions of PM<sub>2.5</sub> and
UFP from kerosene were also low compared with solid fuel burning but
had a relatively high <i>F</i><sub>30</sub> value of approximately
73–80%