Randy L. Maddalena

BETR North America: a regionally segmented multimedia contaminant fate model for North America.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.

Volatile organic compounds in small- and medium-sized commercial buildings in California

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.

Phthalate Exposure and Risk Assessment in California Child Care Facilities

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 Californias 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.

Plant uptake of organic pollutants from soil: Bioconcentration estimates based on models and experiments

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.

Comparison of multi-media transport and transformation models: Regional fugacity model vs. CalTOX

Two multimedia environmental transport and transformation computer models are summarized and compared. The regional fugacity model published by Mackay and Paterson (1991), termed Fug3ONT, is a four compartment steady-state model designed to simulate the relative distribution of nonionic organic chemicals in a multimedia system. CalTOX is a seven compartment multimedia total exposure model for hazardous waste sites. Both models are based on the principles of fugacity. CalTOX, however, separates the soil into three layers (surface, root, and vadose) and uses a different approach to estimate the diffusive mass transfer rate in soil. These differences result in lower estimates of the steady-state contaminant concentrations of six environmentally relevant chemicals in the root soil of CalTOX as compared to the bulk soil of Fug3ONT. The difference is greatest for compounds with low mobility in soil such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin and Benzo(a)pyrene where estimates from CalTOX and Fug3ONT differ by more than 3 orders of magnitude. Otherwise, the models provide similar estimates for the distribution of the six chemicals among the air, water, sediment and surface soil.

Effect of Temperature and Humidity on Formaldehyde Emissions in Temporary Housing Units

ABSTRACT 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. IMPLICATIONS Maddalena et al. reported differences between formalde-hyde concentrations in samples collected from the THUs during the morning and afternoon of the same day, highlighting the need to carry out further analysis on the effect of temperature and humidity on formaldehyde emissions. This study addresses the influence of temperature and humidity on formaldehyde emission factors from individual materials. The information provided can be incorporated into an exposure assessment study for the occupants of the FEMA trailers. However, because the experiments are carried out only on four samples from the THUs, they might not be representative of the entire fleet of THUs.

Rapid and sensitive gas chromatography–ion-trap tandem mass spectrometry method for the determination of tobacco-specific N-nitrosamines in secondhand smoke

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.

Polycyclic aromatic hydrocarbons in edible grain: a pilot study of agricultural crops as a human exposure pathway for environmental contaminants using wheat as a model crop.

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.

Effects of ventilation rate per person and per floor area on perceived air quality, sick building syndrome symptoms, and decision-making

UNLABELLED Ventilation rates (VRs) in buildings must adequately control indoor levels of pollutants; however, VRs are constrained by the energy costs. Experiments in a simulated office assessed the effects of VR per occupant on perceived air quality (PAQ), Sick Building Syndrome (SBS) symptoms, and decision-making performance. A parallel set of experiments assessed the effects of VR per unit floor area on the same outcomes. Sixteen blinded healthy young adult subjects participated in each study. Each exposure lasted four hours and each subject experienced two conditions in a within-subject study design. The order of presentation of test conditions, day of testing, and gender were balanced. Temperature, relative humidity, VRs, and concentrations of pollutants were monitored. Online surveys assessed PAQ and SBS symptoms and a validated computer-based tool measured decision-making performance. Neither changing the VR per person nor changing the VR per floor area, had consistent statistically significant effects on PAQ or SBS symptoms. However, reductions in either occupant-based VR or floor-area-based VR had a significant and independent negative impact on most decision-making measures. These results indicate that the changes in VR employed in the study influence performance of healthy young adults even when PAQ and SBS symptoms are unaffected. PRACTICAL IMPLICATIONS The study results indicate the importance of avoiding low VRs per person and low VRs per floor area to minimize decrements in cognitive performance.

Dependence of intake fraction on release location in a multi-media framework: A case study of four contaminants in North America

The extent of human exposure to persistent anthropogenic environmental contaminants is a complex function of the amount of chemical emitted, its physico-chemical properties and reactivity, the nature of the environment, and the characteristics of the pathways for human exposure, such as inhalation, intake of food and water and dermal contact. For some chemicals, the location of emissions relative to areas of high population density or intense food production may also be an important factor. The relative importance of these variables is explored using the regionally segmented BETR North America contaminant fate model and data for food production patterns and population density for North America. The model is applied to four contaminants emitted to air: benzene, carbon tetrachloride, benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo dioxin. The total continental intake fraction (iF), relating exposure quantity to emission quantity, is employed as a metric for assessing population exposure to environmental contaminants. The results show that the use of continentally averaged parameters for population density and food production provides an accurate estimate of the median of iF calculated for emissions in individual regions, however iF can range from this median by up to 3 orders of magnitude, especially for chemicals transferred to humans through the food pathway. The location of population relative to food production and emissions of chemicals are important variables that should be considered in assessing the public health implications of chemical emissions.