ABSTRACT
The use of household cleaning products can result in exposure to potentially hazardous volatile and semi-volatile organic compounds (VOCs and SVOCs). "Green" cleaning products have become increasingly available, but there is no official "green" standard, and it is difficult for consumers to know what chemicals they may be exposed to while cleaning. We measured air concentrations of 46 VOCs and SVOCs of concern released from conventional and "green" cleaning products during both real-world household cleaning and a controlled chamber environment, with a focus on chemicals that might increase women's risk of breast cancer, including possible carcinogens, reproductive/developmental toxicants, or endocrine disruptors. Air samples were analyzed using gas chromatography-mass spectrometry and high-performance liquid chromatography. First, in a study of 50 women cleaning their own homes using either conventional or "green" cleaning products, we recorded the products used and collected air samples from the breathing zone to determine whether specific products or types of products were associated with increased concentrations of specific VOCs and SVOCs. The results showed that women who used conventional bleach products, disinfecting wipes, and dish soap had higher breathing zone air concentrations of several VOCs, including chloroform, carbon tetrachloride, hexaldahyde, and 1,4-dioxane, than women who did not use these products. While fewer "green" products were associated with increases in VOC air concentrations, use of "green" all-purpose cleaners was associated with increases in air concentrations of some fragrance chemicals of concern. In the laboratory, we then selected 9 of the most common conventional products and 7 "green" products used in the in-home study for measurement of the same VOCs using a continuous stirred cylindrical flow-through chamber. We found that 75% of the highest VOC emissions were emitted by conventional cleaning products, but we also identified VOC emissions of concern from green products. VOC emissions in the chamber largely agreed with the modeled associations from real-world cleaning.
Subject(s)
Air Pollution, Indoor , Volatile Organic Compounds , Female , Humans , Volatile Organic Compounds/analysis , Air Pollution, Indoor/analysis , Gas Chromatography-Mass SpectrometryABSTRACT
BACKGROUND: Household cleaning products may be a significant source of chemical exposures, including carcinogens and suspected endocrine disruptors. OBJECTIVES: We characterized exposures during routine household cleaning and tested an intervention to reduce exposures to cleaning product chemicals. METHODS: The Lifting Up Communities with Interventions and Research (LUCIR) Study is a youth-led, community-based intervention project. Youth researchers conducted personal air monitoring with 50 Latina women while they cleaned their homes with their regular cleaning products (preintervention visit) and then 1 week later while they used "green" cleaning products provided by the study (postintervention visit). Air samples were analyzed for volatile and semivolatile organic compounds using gas chromatography-mass spectrometry and high-performance liquid chromatography. We compared pre- and postintervention air concentrations of 47 chemicals of concern, selected because they were on California's Proposition 65 list of carcinogens or reproductive/developmental toxicants or were suspected endocrine disruptors. Youth researchers were integrally involved in the study design, data collection, interpretation, and dissemination of findings. RESULTS: We observed statistically significant decreases in air concentrations of 17 chemicals of concern when participants switched to green cleaning products, including decreases in geometric mean concentrations of 1,4-dioxane (-46.4%), chloroform (-86.7%), benzene (-24.8%), naphthalene (-40.3%), toluene (-24.2%), and hexane (-35.5%). We observed significant increases in air concentrations of three fragrance compounds: the plant-derived terpene, beta-myrcene (221.5%), and the synthetic musks celestolide (31.0%) and galaxolide (79.6%). Almost all participants (98%) said the replacement products worked as well as their original products, and 90% said that they would consider buying the replacement products in the future. DISCUSSION: This study demonstrates that choosing cleaning products that are marketed as green may reduce exposure to several carcinogens and endocrine disruptors. Future studies should determine whether use of unscented green products would further reduce exposure to terpenes and musks. https://doi.org/10.1289/EHP8831.
Subject(s)
Endocrine Disruptors , Hazardous Substances , Adolescent , Female , Gas Chromatography-Mass Spectrometry , Hispanic or Latino , Humans , Organic ChemicalsABSTRACT
"Sub-ohm" atomizers with reduced resistance can deliver more power than conventional electronic cigarettes. Typical battery outputs are 100 W or more. These devices are particularly popular among young users, and can be a significant source of volatile carbonyls in the indoor environment. Emissions from next-generation sub-ohm vaping products were characterized by determining e-liquid consumption and volatile aldehydes emissions for several combinations of popular high-power configurations. Tests explored the effect of dilution air flow (air vent opening), puffing volume, and coil assembly configuration. The mass of liquid consumed per puff increased as the puff volume increased from 50 to 100 mL, then remained relatively constant for larger puff volumes up to 500 mL. This is likely due to mass transfer limitations at the wick and coil assembly, which reduced the vaporization rate at higher puff volumes. Carbonyl emission rates were systematically evaluated using a 0.15 Ω dual coil atomizer as a function of the puffing volume and dilution air flow, adjusted by setting the air vents to either 100% (fully open), 50%, 25%, or 0% (closed). The highest formaldehyde emissions were observed for the lowest puff volume (50 mL) when the vents were closed (48 ng mg-1), opened at 25% (39 ng mg-1) and at 50% (32 ng mg-1). By contrast, 50-mL puffs with 100% open vents, and puff volumes >100 mL for any vent aperture, generated formaldehyde yields of 20 ng mg-1 or lower, suggesting that a significant cooling effect resulted in limited carbonyl formation. Considering the effect of the coil resistance when operated at a voltage of 3.8 V, the amount of liquid evaporated per puff decreased as the resistance increased, in the order of 0.15 Ω > 0.25 Ω > 0.6 Ω, consistent with decreasing aerosol temperatures measured at the mouthpiece. Three different configurations of 0.15 Ω coils (dual, quadruple and octuple) were evaluated, observing significant variability. No clear trend was found between carbonyl emission rates and coil resistance or configuration, with highest emissions corresponding to a 0.25 Ω dual coil atomizer. Carbonyl emission rates were compared with those determined using the same methodology for conventional e-cigarettes (lower power tank systems), observing overall lower yields for the sub-ohm devices.
Subject(s)
Electronic Nicotine Delivery Systems , Tobacco Products , Vaping , Aerosols , AldehydesABSTRACT
Vaporizable cannabis concentrates (VCCs) consumed as a liquid (vaping) or a waxy solid (dabbing) are becoming increasingly popular. However, their associated emissions and impacts have not been fully described. Mixtures containing different proportions of 12 VCC terpenoids and high MW compounds were heated at 100-500 °C inside a room-sized chamber to simulate emissions. Terpenoids, thermal degradation byproducts, and ultrafine particles (UFPs) were quantified in the chamber air. Air samples contained over 50% of emitted monoterpenes and less than 40% of released sesquiterpenes and terpene alcohols. Eleven degradation byproducts were quantified, including acrolein (1.3-3.9 µg m-3) and methacrolein (2.0 µg m-3). A large amount of UFPs were released upon heating and remained airborne for at least 3 h. The mode diameter increased from 80 nm at 100 °C to 140 nm at 500 °C, and particles smaller than 250 nm contributed to 90% of PM1.0. The presence of 0.5% of lignin, flavonoid, and triterpene additives in the heated mixtures resulted in a threefold increase in the particle formation rate and PM1.0 concentration, suggesting that these high-molecular-weight compounds enhanced aerosol inception and growth. Predicted UFP emission rates in typical consumption scenarios (6 × 1011-2 × 1013 # min-1) were higher than, or comparable with, other common indoor sources such as smoking and cooking.
Subject(s)
Air Pollutants , Air Pollution, Indoor , Cannabis , Aerosols , Air Pollutants/analysis , Air Pollution, Indoor/analysis , Cooking , Environmental Monitoring , Particle Size , Particulate Matter/analysis , TerpenesABSTRACT
Ozonation is a common remediation approach to eliminate odors from mold, tobacco and fire damage in buildings. Little information exists to: 1) assess its effectiveness; 2) provide guidance on operation conditions; and 3) identify potential risks associated with the presence of indoor ozone and ozonation byproducts. The goal of this study is to evaluate chemical changes in thirdhand smoke (THS) aerosols induced by high levels of ozone, in comparison with THS aerosols aged under similar conditions in the absence of ozone. Samples representing different stages of smoke aging in the absence of ozone, including freshly emitted secondhand smoke (SHS) and THS, were collected inside an 18-m3 room-sized chamber over a period of 42 h after six cigarettes were consumed. The experiments involved collection and analysis of gas phase species including volatile organic compounds (VOCs), volatile carbonyls, semivolatile organic compounds (SVOCs), and particulate matter. VOC analysis was carried out by gas chromatography/mass spectrometry with a thermal desorption inlet (TD-GC/MS), and volatile carbonyls were analyzed by on-line derivatization with dinitrophenylhydrazine (DNPH), followed by liquid chromatography with UV/VIS detection. SVOCs were extracted from XAD-coated denuders and Teflon-coated fiberglass filters in the absence of ozone. In those extracts, tobacco-specific nitrosamines (TSNAs) and other SVOCs were analyzed by gas chromatography with positive chemical ionization-triple quadrupole mass spectrometric detection (GC/PCI-QQQ-MS), and polycyclic aromatic hydrocarbons (PAHs) were quantified by gas chromatography with ion trap mass spectrometric detection (GC/IT-MS) in selected ion monitoring mode. Particulate matter concentration was determined gravimetrically. In a second experiment, a 300 mg h-1 commercial ozone generator was operated during 1 h, one day after smoke was generated, to evaluate the remediation of THS by ozonation. VOCs and volatile carbonyls were analyzed before and after ozonation. Extracts from fabrics that were exposed in the chamber before and after ozonation as surrogates for indoor furnishings were analyzed by GC/IT-MS, and aerosol size distribution was studied with a scanning mobility particle sizer. Ozone concentration was measured with a photometric detector. An estimated 175 mg ozone reacted with THS after 1 h of treatment, corresponding to 58% of the total O3 released during that period. Fabric-bound nicotine was depleted after ozonation, and the surface concentration of PAHs adsorbed to fabric specimens decreased by an order of magnitude due to reaction with ozone, reaching pre-smoking levels. These results suggest that ozonation has the potential to remove harmful THS chemicals from indoor surfaces. However, gas phase concentrations of volatile carbonyls, including formaldehyde, acetaldehyde and acetone were higher immediately after ozonation. Ultrafine particles (UFP, in most cases with size <60 nm) were a major ozonation byproduct. UFP number concentrations peaked shortly after ozonation ended, and remained at higher-than background levels for several hours. Based on these results, minimum re-entry times after ozone treatment were predicted for different indoor scenarios. Clearly defining re-entry times can serve as a practical measure to prevent acute exposures to ozone and harmful ozonation byproducts after treatment. This study evaluated potential benefits and risks associated with THS remediation using ozone, providing insights into this technology.
Subject(s)
Ozone , Percutaneous Coronary Intervention , Tobacco Smoke Pollution , Gas Chromatography-Mass Spectrometry , Smoke , Nicotiana , Tobacco Smoke Pollution/analysisABSTRACT
Dry anaerobic digestion (AD) of organic municipal solid waste (MSW) followed by composting of the residual digestate is a waste diversion strategy that generates biogas and soil amendment products. The AD-composting process avoids methane (CH4) emissions from landfilling, but emissions of other greenhouse gases, odorous/toxic species, and reactive compounds can affect net climate and air quality impacts. In situ measurements of key sources at two large-scale industrial facilities in California were conducted to quantify pollutant emission rates across the AD-composting process. These measurements established a strong relationship between flared biogas ammonia (NH3) content and emitted nitrogen oxides (NOx), indicating that fuel NOx formation is significant and dominates over the thermal or prompt NOx pathways when biogas NH3 concentration exceeds â¼200 ppm. Composting is the largest source of CH4, carbon dioxide (CO2), nitrous oxide (N2O), and carbon monoxide (CO) emissions (â¼60-70%), and dominate NH3, hydrogen sulfide (H2S), and volatile organic compounds (VOC) emissions (>90%). The high CH4 contribution to CO2-equivalent emissions demonstrates that composting can be an important CH4 source, which could be reduced with improved aeration. Controlling greenhouse gas and toxic/odorous emissions from composting offers the greatest mitigation opportunities for reducing the climate and air quality impacts of the AD-composting process.
Subject(s)
Air Pollutants , Composting , Greenhouse Gases , Air Pollutants/analysis , Anaerobiosis , Carbon Dioxide/analysis , Greenhouse Effect , Greenhouse Gases/analysis , Methane/analysis , Nitrous Oxide/analysis , Solid WasteABSTRACT
Microalgae produce specific chemicals indicative of stress and/or death. The aim of this study was to perform non-destructive monitoring of algal culture systems, in the presence and absence of grazers, to identify potential biomarkers of incipient pond crashes. Here, we report ten volatile organic compounds (VOCs) that are robustly generated by the marine alga, Microchloropsis salina, in the presence and/or absence of the marine grazer, Brachionus plicatilis. We cultured M. salina with and without B. plicatilis and collected in situ volatile headspace samples using thermal desorption tubes over the course of several days. Data from four experiments were aggregated, deconvoluted, and chromatographically aligned to determine VOCs with tentative identifications made via mass spectral library matching. VOCs generated by algae in the presence of actively grazing rotifers were confirmed via pure analytical standards to be pentane, 3-pentanone, 3-methylhexane, and 2-methylfuran. Six other VOCs were less specifically associated with grazing but were still commonly observed between the four replicate experiments. Through this work, we identified four biomarkers of rotifer grazing that indicate algal stress/death. This will aid machine learning algorithms to chemically define and diagnose algal mass production cultures and save algae cultures from imminent crash to make biofuel an alternative energy possibility.
ABSTRACT
Infants and young children spend as much as 50h per week in child care and preschool. Although approximately 13 million children, or 65% of all U.S. children, spend some time each day in early childhood education (ECE) facilities, little information is available about environmental exposures in these environments. We measured flame retardants in air and dust collected from 40 California ECE facilities between May 2010 and May 2011. Low levels of six polybrominated diphenyl ether (PBDE) congeners and four non-PBDE flame retardants were present in air, including two constituents of Firemaster 550 and two tris phosphate compounds [tris (2-chloroethyl) phosphate (TCEP) and tris (1,3-dichloroisopropyl) phosphate (TDCIPP)]. Tris phosphate, Firemaster 550 and PBDE compounds were detected in 100% of the dust samples. BDE47, BDE99, and BDE209 comprised the majority of the PBDE mass measured in dust. The median concentrations of TCEP (319 ng g(-1)) and TDCIPP (2265 ng g(-1)) were similar to or higher than any PBDE congener. Levels of TCEP and TDCIPP in dust were significantly higher in facilities with napping equipment made out of foam (Mann-Whitney p-values<0.05). Child BDE99 dose estimates exceeded the RfD in one facility for children<3 years old. In 51% of facilities, TDCIPP dose estimates for children<6 years old exceeded age-specific "No Significant Risk Levels (NSRLs)" based on California Proposition 65 guidelines for carcinogens. Given the overriding interest in providing safe and healthy environments for young children, additional research is needed to identify strategies to reduce indoor sources of flame retardant chemicals.
Subject(s)
Air Pollutants/analysis , Air Pollution, Indoor/analysis , Dust/analysis , Environmental Exposure/analysis , Flame Retardants/analysis , California , Child Day Care Centers , Child, Preschool , Female , Halogenated Diphenyl Ethers/analysis , Housing , Humans , Male , Organophosphates/analysis , Risk Assessment , Schools , United StatesABSTRACT
Approximately 13 million U.S. children less than 6 years old spend some time in early childhood education (ECE) facilities where they may be exposed to potentially harmful chemicals during critical periods of development. We measured five phthalate esters in indoor dust (n = 39) and indoor and outdoor air (n = 40 and 14, respectively) at ECE facilities in Northern California. Dust and airborne concentrations were used to perform a probabilistic health risk assessment to compare estimated exposures with risk levels established for chemicals causing reproductive toxicity and cancer under California's Proposition 65. Di(2-ethylhexyl) phthalate (DEHP) and butyl benzyl phthalate (BBzP) were the dominant phthalates present in floor dust (medians = 172.2 and 46.8 µg/g, respectively), and dibutyl phthalate (DBP), diethyl phthalate (DEP), and diisobutyl phthalate (DIBP) were the dominant phthalates in indoor air (medians = 0.52, 0.21, and 0.10 µg/m(3), respectively). The risk assessment results indicate that 82-89% of children in California ECE had DBP exposure estimates exceeding reproductive health benchmarks. Further, 8-11% of children less than 2 years old had DEHP exposure estimates exceeding cancer benchmarks. This is the largest study to measure phthalate exposure in U.S. ECE facilities and findings indicate wide phthalate contamination and potential risk to developing children.
Subject(s)
Child Day Care Centers , Environmental Exposure/analysis , Phthalic Acids/analysis , Risk Assessment , Air/analysis , Air Pollution, Indoor/analysis , California , Child , Child, Preschool , Computer Simulation , Dust/analysis , Humans , Humidity , Infant , Maximum Allowable Concentration , Monte Carlo Method , Neoplasms/pathology , Reproductive Health , Statistics, Nonparametric , TemperatureABSTRACT
While small- and medium-sized commercial buildings (SMCBs) make up 96% of the commercial buildings in the U.S., serving a large variety of uses, little information is available on indoor air quality (IAQ) in SMCBs. This study investigated 37 SMCBs distributed across different sizes, ages, uses, and regions of California. We report indoor concentrations and whole building emission rates of a suite of 30 VOCs and aldehydes in these buildings. There was a considerable range in the concentrations for each of the contaminants, especially for formaldehyde, acetaldehyde, decamethylcyclopentasiloxane, d-limonene, 2-butoxyethanol, toluene, 2,2,4-trimethylpentanediol diisobutyrate, and diethylphthalate. The cause of higher concentrations in some building categories generally corresponded to expected sources, for example, chloroform was higher in restaurants and grocery stores, and formaldehyde was higher in retail stores and offices. Factor analysis suggests sources in SMCBs include automobile/traffic, cleaning products, occupant sources, wood products/coating, and plasticizers. The comparison to health guidelines showed that formaldehyde concentrations were above the chronic RELs required by the OEHHA (9 µg/m³) in 86% of the buildings. Data collected in this study begins to fill the knowledge gap for IAQ in SMCBs and helps us understand the indoor sources of VOCs to further improve indoor air quality in SMCBs.
Subject(s)
Air Pollution, Indoor/analysis , Volatile Organic Compounds/analysis , Aldehydes , Environmental MonitoringABSTRACT
The effect of temperature and humidity on formaldehyde emissions from samples collected from temporary housing units (THUs) was studied. The THUs were supplied by the U.S. Federal Emergency Management Administration (FEMA) to families that lost their homes in Louisiana and Mississippi during the Hurricane Katrina and Rita disasters. On the basis of a previous study, four of the composite wood surface materials that dominated contributions to indoor formaldehyde were selected to analyze the effects of temperature and humidity on the emission factors. Humidity equilibration experiments were carried out on two of the samples to determine how long the samples take to equilibrate with the surrounding environmental conditions. Small chamber experiments were then conducted to measure emission factors for the four surface materials at various temperature and humidity conditions. The samples were analyzed for formaldehyde via high-performance liquid chromatography. The experiments showed that increases in temperature or humidity contributed to an increase in emission factors. A linear regression model was built using the natural log of the percent relative humidity (RH) and inverse of temperature (in K) as independent variables and the natural log of emission factors as the dependent variable. The coefficients for the inverse of temperature and log RH with log emission factor were found to be statistically significant for all of the samples at the 95% confidence level. This study should assist in retrospectively estimating indoor formaldehyde exposure of occupants of THUs.
Subject(s)
Air Pollution, Indoor/analysis , Construction Materials/analysis , Formaldehyde/chemistry , Humidity , Temperature , Emergencies , Environmental Monitoring , Housing , United StatesABSTRACT
Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs adsorbed to model surfaces and secondhand smoke (SHS) particles using gas chromatography-ion-trap tandem mass spectrometry. In an 18-m(3) room-sized chamber, a smoking machine generated realistic concentrations of SHS that were actively sampled on Teflon-coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid-liquid extraction protocol using methanol as solvent was successfully applied to both substrates with recoveries ranging from 85 to 115%. For each TSNA, tandem MS parameters were optimized and the major fragmentation pathways were elucidated. The method showed excellent performance, with a linear dynamic range from 2 to 1000ngmL(-1), low detection limits (S/N>3) of 30-300pgmL(-1) and precision with experimental errors below 10% for all compounds. Moreover, no interfering peaks were observed, indicating a high selectivity of MS/MS without the need for a sample clean-up step. This method provides a suitable analytical tool to detect and quantify traces of TSNA in indoor environments polluted with SHS.
Subject(s)
Gas Chromatography-Mass Spectrometry/methods , Nicotiana/chemistry , Nitrosamines/chemistry , Tobacco Smoke Pollution/analysis , Sensitivity and Specificity , Tandem Mass Spectrometry/methodsABSTRACT
Indoor concentrations of 33 volatile organic chemicals were measured in four unoccupied temporary housing units (THUs) belonging to the U.S. Federal Emergency Management Administration (FEMA). The highest level contaminants in the THUs include formaldehyde, acetic acid, and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) with median concentrations of 440, 425, and 36 ppb, respectively. A number of volatile organic compounds (VOCs) were higher than published concentrations in other dwellings, but whole THU emission factors for most chemicals were either lower than or similar to values reported for newly constructed homes. However, several chemicals exceeded previously measured new building emission rates by over a factor of 5. Materials were collected from the THUs, and emission factors were determined using small chambers to identify the potential source of indoor contaminants. The individual materials were grouped by material type, and emissions were used to derive exposure concentrations for comparison to reference values. Using material loading factors and ventilation rates that are relevant to the trailers, all of the material types we tested had at least two chemicals (formaldehyde and nonanal) with derived concentrations in excess of chronic reference exposure levels or odor thresholds. The extensive use of composite wood products, sealants, and vinyl coverings, combined with the low air exchange rates relative to material surface areas, may explain the high concentrations of some VOCs and formaldehyde.
Subject(s)
Air Pollution, Indoor/analysis , Environmental Monitoring/methods , Formaldehyde/analysis , Housing , Volatile Organic Compounds/analysis , Acetic Acid/analysis , Air Pollutants/analysis , Butyrates/analysis , Environmental Exposure , Environmental Pollutants/analysis , Reference Values , Time Factors , Vehicle Emissions/toxicity , VentilationABSTRACT
Present and future concentrations of DDT in the environment are calculated with the global multimedia model CliMoChem. Monte Carlo simulations are used to assess the importance of uncertainties in substance property data, emission rates, and environmental parameters for model results. Uncertainties in the model results, expressed as 95% confidence intervals of DDT concentrations in various environmental media, in different geographical locations, and at different points in time are typically between 1 and 2 orders of magnitude. An analysis of rank correlations between model inputs and predicted DDT concentrations indicates that emission estimates and degradation rate constants, in particular in the atmosphere, are the most influential model inputs. For DDT levels in the Arctic, temperature dependencies of substance properties are also influential parameters. A Bayesian Monte Carlo approach is used to update uncertain model inputs based on measurements of DDT in the field. The updating procedure suggests a lower value for half-life in air and a reduced range of uncertainty for Kow of DDT. As could be expected, the Bayesian updating yields model results that are closer to observations, and model uncertainties have decreased. Sensitivity analysis and Bayesian Monte Carlo approach in combination provide new insight into important processes that govern the global fate and persistence of DDT in the environment.
Subject(s)
DDT/analysis , Environment , Models, Statistical , Uncertainty , Air , Arctic Regions , Bayes Theorem , Monte Carlo Method , SoilABSTRACT
The concentrations of polycyclic aromatic hydrocarbons (PAHs) were investigated in a pilot study of field wheat grain as a model indicator for environmental contamination. The edible grain would serve as a portal for human exposure. Wheat grain was initially studied since it is one of the major food crops consumed internationally by many including infants and children. Wheat grain samples from five different geographical growing locations in California that span approximately 450 km were collected during the same growing season. The same variety of grain was harvested and analyzed for PAHs that ranged from 2- to 6-rings. PAHs were detected in all grain samples and were mainly 2- to 4-ring PAHs with naphthalene the most abundant among them. There were geographical differences in the levels of PAHs in the grain. The sources of the PAHs were not known in this pilot study, but the principal component analysis indicates that the major source is similar in all locations except for naphthalene. Grain naphthalene concentrations may reflect local naphthalene emissions. Diesel-fueled harvesting operations did not appear to contribute to the observed PAH concentrations in the grain. An estimate of naphthalene intake from eating grain compared to inhalation intake demonstrated the potential importance of field contamination of grain as a possible portal of human exposure. The relationship between PAH concentrations in grain and air should be quantitatively investigated to better quantitate exposure and to identify effective measures to lower the risk from PAH exposure through eating grain.
Subject(s)
Crops, Agricultural/chemistry , Environmental Exposure/analysis , Polycyclic Aromatic Hydrocarbons/analysis , Triticum/chemistry , Agriculture/instrumentation , Atmosphere , California , Eating , Gasoline , Geography , Humans , Naphthalenes , Pilot ProjectsABSTRACT
Polycyclic aromatic hydrocarbons (PAHs) can partition from the atmosphere into agricultural crops, contributing to exposure through the dietary pathway. In this study, controlled environmental chamber experiments were conducted to investigate the transfer of PAHs from air into wheat grain, which is a major food staple. A series of PAHs ranging in size from naphthalene to pyrene were maintained at elevated gas-phase concentrations in the chamber housing mature and dry wheat grain both on the plant and with the husk removed. The PAHs did not achieve equilibrium between the air and grain over the 6.5 month monitoring period used in this study. Therefore, PAH uptake under field conditions is expected to be kinetically limited. A clearance study conducted for the grain showed the half-life of clearance was approximately 20 days for all compounds studied. The results suggest that atmospheric contaminants that partition into grain may remain in the grain long enough to contribute to dietary exposure for humans. Mass transfer across the air/grain interface appeared to be limited by grain-side resistance. The grain may act as a multicompartment system with rapid exchange at the surface followed by slower transfer into the grain. A grain/air concentration relationship was derived for the uptake time that is relevant to field conditions.
Subject(s)
Air Pollutants/analysis , Edible Grain/metabolism , Environmental Monitoring/methods , Polycyclic Aromatic Hydrocarbons/analysis , Triticum/metabolism , Agriculture , Air , Diet , Diffusion , Environmental Exposure , Equipment Design , Fluorenes/analysis , Humans , Naphthalenes/analysis , Naphthalenes/chemistry , Plants/metabolism , Pyrenes/analysis , Pyrenes/chemistry , Time FactorsABSTRACT
The role of terrestrial vegetation in transferring chemicals from soil and air into specific plant tissues (e.g., stems, leaves, and roots) is still not well characterized. We provide here a critical review of plant-to-soil bioconcentration ratio (BCR) estimates based on models and experimental data. This review includes the conceptual and theoretical formulations of the BCR, constructing and calibrating empirical and mathematical algorithms to describe this ratio and the experimental data used to quantify BCRs and calibrate the model performance. We first evaluate the theoretical basis for the BCR concept and BCR models and consider how lack of knowledge and data limit reliability and consistency of BCR estimates. We next consider alternate modeling strategies for BCR. A key focus of this evaluation is the relative contributions to overall uncertainty from model uncertainty versus variability in the experimental data used to develop and test the models. As a case study, we consider a single chemical, hexahydro-1,3,5-trinitro-1,3,5-triazine, and focus on variability of bioconcentration measurements obtained from 81 experiments with different plant species, different plant tissues, different experimental conditions, and different methods for reporting concentrations in the soil and plant tissues. We use these observations to evaluate both the magnitude of experimental variability in plant bioconcentration and compare this to model uncertainty. Among these 81 measurements, the variation of the plant-to-soil BCR has a geometric standard deviation (GSD) of 3.5 and a coefficient of variation (CV; i.e., ratio of the arithmetic standard deviation to the mean) of 1.7. These variations are significant but low relative to model uncertainties, which have an estimated GSD of 10, with a corresponding CV of 14.
Subject(s)
Models, Biological , Plant Structures/chemistry , Plant Structures/metabolism , Soil Pollutants/analysis , Soil Pollutants/pharmacokinetics , Plant Structures/growth & development , Sensitivity and Specificity , Soil Pollutants/isolation & purification , Tissue DistributionABSTRACT
Mass balance models of chemical fate and transport can be applied in ecological risk assessments for quantitative estimation of concentrations in air, water, soil, and sediment. These concentrations can, in turn, be used to estimate organism exposures and ultimately internal tissue concentrations that can be compared to mode-of-action-based critical body residues that induce toxic effects. From this comparison, risks to the exposed organism can be evaluated. To demonstrate the use of fate models in ecological risk assessment, we combine the EQuilibrium Criterion (EQC) environmental fate model with a simple screening level biouptake model for three representative organisms: a bird, a mammal, and a fish. This effort yields estimates of internal body concentrations that can be compared with levels known to elicit toxic effects. As an illustration, we present an analysis of 24 hydrocarbon components of gasoline that differ in properties but are assumed to elicit toxicity by a common narcotic mode of action. Results demonstrate that differences in chemical properties and mode of entry into the environment lead to profound differences in the efficiency of transport from emission to target biota. We discussthe implications of these results and draw attention to the insights gained about regional fate and ecological risks associated with gasoline. This approach is suitable for assessing single chemicals or mixtures that have similar modes of action. We conclude that the model-based methodologies presented are widely applicable for screening level ecological risk assessments that support effective chemicals management.
Subject(s)
Ecology , Environmental Exposure , Environmental Pollutants/metabolism , Gasoline/toxicity , Hydrocarbons/metabolism , Animals , Biodiversity , Birds/metabolism , Environmental Pollutants/toxicity , Fishes/metabolism , Geologic Sediments/chemistry , Hydrocarbons/toxicity , Models, Biological , Narcotics/metabolism , Narcotics/toxicity , Risk Assessment , Time FactorsABSTRACT
The effectiveness of a probabilistic risk assessment (PRA) depends on the quality and relevance of the output from exposure and risk models, which, in turn, depends on the critical inputs to the assessment. These critical inputs are often in the form of probabilistic exposure factor distributions that are derived for the given risk scenario. Deriving probabilistic distributions for model inputs can be time consuming and subjective. The absence of a standard approach for developing these distributions can result in PRAs that are inconsistent and difficult to review by regulatory agencies. We present an approach that reduces subjectivity in the distribution development process without limiting the flexibility needed to prepare relevant PRAs. The approach requires two steps. First, we analyze data pooled at a population scale to (i) identify the most robust demographic descriptors within the population for a given exposure factor, (ii) partition the data into subsets based on these variables, and (iii) construct archetypal distributions for each subpopulation. Second, we sample from these archetypal distributions according to site- or scenario-specific conditions to simulate exposure factor values and use these values to construct the scenario-specific input distribution. The archetypal distributions developed through Step 1 provide a consistent basis for developing scenario-specific distributions so risk assessors will not have to repeatedly collect and analyze raw data for each new assessment. We demonstrate the approach for two commonly used exposure factors--body weight (BW) and exposure duration (ED)--using data that are representative of the U.S. population. For these factors we provide a first set of subpopulation-based archetypal distributions and demonstrate methods for using these distributions to construct relevant scenario-specific probabilistic exposure factor distributions.
Subject(s)
Environmental Exposure , Adolescent , Adult , Aged , Body Weight , Child , Child, Preschool , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Models, Statistical , Risk AssessmentABSTRACT
Both laboratory and field studies confirm the importance of vegetation for scavenging semivolatile organic chemicals (SVOCs) from the atmosphere and a number of exposure studies have found that the dietary pathway is often a significant contributor to cumulative exposure for these chemicals. However, little information exists on the atmospheric source-to-dietary intake linkage for SVOCs. Because of higher SVOC emissions to urban regions, this linkage is particularly important for foods that are grown, distributed and consumed in or near urban regions. The food pathway can also contribute to dietary exposure for populations that are remote from a pollutant source if the pollutants can migrate to agricultural regions and subsequently to the agricultural commodities distributed to that population. We use available data, the characteristic travel distance, and the CalTOX multimedia model framework to assess the contribution of local sources of food to cumulative SVOC intake. Based on published concentration data for foods, our exposure calculations indicate that the potential intake through ingestion can be up to 1000 times that of inhalation for certain persistent SVOCs. We use the population-based intake fraction (iF) to determine how SVOC intake can vary among food commodities and exposure pathways, and to determine the contribution of airborne emitted SVOCs to the diet in the Northern Hemisphere. We focus on three representative multimedia SVOCs-benzo(a)pyrene, fluoranthene, and 2,3,7,8-tetrachlorodibenzo-p-dioxin. The approach presented here provides a useful framework and starting point for source-to-intake assessments for the ambient air-to-dietary exposure pathway.