Multimedia Exposure Model Research Articles

Mapping blood lead levels in French children due to environmental contamination using a modeling approach

The decrease in levels of lead in air and drinking water over the last 40 years has resulted in an overall decrease in blood lead levels (BLLs). However, there is no known safe level of lead regarding developmental effects in children. This paper maps predicted BLLs of children in France, resulting from a simulated chronic exposure in two steps, with the aim of identifying areas with environmentally overexposed populations. Probabilistic estimates of BLLs based on environmental contamination were obtained and compared to biomonitoring data. First, the contribution of various environmental exposure pathways was estimated using a multimedia exposure model: spatialized data on soil, drinking water and air contamination, together with data on food contamination and ingestion, was joined using geostatistical approaches. In a second step, a Physiologically Based Toxicokinetic (PBTK) model provided estimates of BLLs. Probabilistic estimates of BLLs were obtained by simulating uncertainty and variability of exposure levels, physiological characteristics and lead-specific parameters in the PBTK model.The median and 95th percentile of predicted BLLs in children aged 1 to 11 were compared to recent biomonitoring data obtained in France in young children (SATURNINF study): median predictions were overestimated in infants and in agreement with median observed BLLs in children aged 3 to 6. Upper bounds of predicted BLLs were protective due to uncertainties in exposure estimates. The main source of exposure appeared to be drinking water in children over 2 years old, and vegetal food and milk in children under 2 years old. Although elevated drinking water lead levels were not related to large geographical areas, the relatively fine resolution map also pinpointed geographical areas of concern due to elevated soil lead levels.

Multi-directional selective toxicity effects on farmland ecosystems: A novel design of green substitutes for neonicotinoid insecticides

Environmental enrichment abilities and chronic sub-lethal effects on non-target organisms caused by neonicotinoid insecticides (neonics) have been challenging issues for environmental pollution. In other words, the renewal of insecticides, especially the research of green substitutes, is one of the best ways to protect the environment and non-target organisms. In this research, a complete design and screening system for green substitutes of neonics was established through the contour map, homology modeling, molecular docking, and molecular dynamics. Contour maps were constructed to obtain the substituted sites and groups, and the results revealed that introducing large, negative/positive or hydrophobic groups can reduce the enrichment abilities of neonics. Using Compound 18 as a template, 58 derivatives with lower enrichment abilities were designed (decreased by 0.55%–57.42%). Then, human health risks were assessed based on multimedia exposure model of pollutants, and the HI values of five derivatives were found to be < 1 and the RI values were <1 × 10−6, indicating that the non-carcinogenic risks of the neonics derivatives were completely acceptable, and the carcinogenic risks were negligible. Furthermore, the multi-selective toxicity of five derivatives in farmland ecosystems was studied using homology modeling and molecular docking, and Derivative-1, Derivative-3, Derivative-10, and Derivative-56 showed multi-selective toxicity on farmland ecosystems. Specifically, the toxicity effects on pests and grubs were enhanced (increased by 1.44%–12.58%), whereas the chronic sublethal effects on bees and earthworms were reduced (decreased by 0.29%–27.18%). Finally, the damage to soybean leaves caused by four derivatives was analyzed by molecular dynamics, and the solvent accessible surface area of the above four derivatives was found to be smaller than that of Compound 18, indicating that the derivatives decomposed more easily in soybean crops, thus reducing the damage to the soybean’s leaf surface. This study provides a significance reference in designing green substitutes for neonics to protect the environment and ecosystem.

Characterization of Environmental Health Inequalities Due to Polyaromatic Hydrocarbon Exposure in France.

Reducing environmental health inequalities has become a major focus of public health efforts in France, as evidenced by the French action plans for health and the environment. To evaluate environmental inequalities, routine monitoring networks provide a valuable source of data on environmental contamination, which can be used in integrated assessments, to identify overexposed populations and prioritize actions. However, available databases generally do not meet sufficient spatial representativeness to characterize population exposure, as they are usually not assembled for this specific purpose. The aim of this study was to develop geoprocessing procedures and statistical methods to build spatial environmental variables (water, air, soil, and food pollutant concentrations) at a fine resolution, and provide appropriate input for the exposure modelling. Those methods were designed to combine in situ monitoring data with correlated auxiliary information (for example, atmospheric emissions, population, and altitude), in order to better represent the variability of the environmental compartment quality. The MODUL’ERS multimedia exposure model developed by INERIS (French Institute for industrial Environment and Risks) was then used to assess the transfer of substances from the environment to humans, through inhalation and ingestion pathway characterization. We applied the methodology to a carcinogenic Polycyclic Aromatic Hydrocarbon substance, benzo[a]pyrene(B[a]P), to map spatialized exposure indicators, at the national scale. The largest environmental contribution corresponded to the ingestion pathway. Data processing algorithms and calculation of exposure will be integrated into the French coordinated integrated environment and health platform PLAINE (PLteforme intégrée d’Analyse des INégalités Environnementales) which has been developed to map and analyze environmental health inequalities.

Assessing Cancer Risk in China from γ-Hexachlorocyclohexane Emitted from Chinese and Indian Sources

Three models, including an atmospheric transport model, a multimedia exposure model, and a risk assessment model, were used to assess cancer risk in China caused by γ-HCH (gamma-hexachlorocyclohexane) emitted from Chinese and Indian sources. Extensive model investigations revealed the contribution of different sources to the cancer risk in China. Cancer risk in Eastern China was primarily attributable to γ-HCH contamination from Chinese sources, whereas cancer risk in Western China was caused mostly by Indian emissions. The contribution of fresh use of lindane in India to the cancer risk in China was almost 1 order of magnitude higher than that of the reemission of γ-HCH from Indian soils. Of total population, 58% (about 0.79 billion) residents in China were found to live in the environment with high levels of cancer risk exceeding the acceptable cancer risk of 10(-6), recommended by the United States Environmental Protection Agency (U.S. EPA). The cancer risk in China was mostly induced by the local contamination of γ-HCH emitted from Chinese sources, whereas fresh use of lindane in India will become a significant source of the cancer risk in China if Indian emissions maintain their current levels.

River water contaminated with perfluorinated compounds potentially posing the greatest risk to young children

Although, humans are exposed to perflourinated compounds (PFCs) from various media, water consumption could be an important source for the residents living near to contaminated areas. Since comprehensive multimedia exposure model has not been developed for PFCs, assessment of the potential risk due to exposure to PFCs through direct water consumption could be a conservative estimate. The human health risks derived from the exposure to PFCs through water consumption were assessed for different age groups of general population in Taiwan using probabilistic approach. Based on available data on concentrations of PFCs in river water, exposure to PFOS, PFOA and PFDA via water consumption for different age groups were calculated using deterministic and probabilistic risk assessment methods. The oral non-cancer risks from PFOS, PFOA and their combination, expressed as a Hazard Index (HI), was determined by comparing oral exposure dose (through water intake) with the oral Reference Dose (RfD). The average exposure to PFOS, PFOA and PFDA via water consumption for adults ranged from 0.16 to 220.15, 0.43 to 12.5 and 0.43 to 2.36ngkg-bw−1d−1 and for children 0.13–354.3, 0.35–20.17 and 0.35–3.79ngkg-bw−1d−1, respectively. Probabilistic values of total HIs for all age groups reside near to Keya River exceed the RfD 2.4–4.8 times, corresponding mainly to PFOS with a percentage of 97%. In conclusions, children aged 1–3years old and the residents reside near to Keya River are at the highest risk of exposure to PFCs via water consumption.

Development of a spatial stochastic multimedia exposure model to assess population exposure at a regional scale

Analyzing the relationship between the environment and health has become a major focus of public health efforts in France, as evidenced by the national action plans for health and the environment. These plans have identified the following two priorities:-identify and manage geographic areas where hotspot exposures are a potential risk to human health; and-reduce exposure inequalities.The aim of this study is to develop a spatial stochastic multimedia exposure model for detecting vulnerable populations and analyzing exposure determinants at a fine resolution and regional scale. A multimedia exposure model was developed by INERIS to assess the transfer of substances from the environment to humans through inhalation and ingestion pathways. The RESPIR project adds a spatial dimension by linking GIS (Geographic Information System) to the model. Tools are developed using modeling, spatial analysis and geostatistic methods to build and discretize interesting variables and indicators from different supports and resolutions on a 1-km2 regular grid.We applied this model to the risk assessment of exposure to metals (cadmium, lead and nickel) using data from a region in France (Nord-Pas-de-Calais). The considered exposure pathways include the atmospheric contaminant inhalation and ingestion of soil, vegetation, meat, egg, milk, fish and drinking water. Exposure scenarios are defined for different reference groups (age, dietary properties, and the fraction of food produced locally).The two largest risks correspond to an ancient industrial site (Metaleurop) and the Lille agglomeration. In these areas, cadmium, vegetation ingestion and soil contamination are the principal determinants of the computed risk.

Environmental and health risk assessment of an oil contaminated site in the Mexican tropical southeast

The aim of the present study was the environmental and health risk assessment of the oil contaminated soil in the Mexican tropic. The case is based on the total petroleum hydrocarbons (TPH) and polycyclic aromatic (PAH) soil contamination resulting from the activities of the oil industry over 70 years. The results of this study were estimated using CalTOX, a multimedia exposure model. The aromatic fraction constituted by PAH of two, three, four and five rings presented concentrations from 0.005 to 3.84 mg/kg. The BaP was the chemical of major concern due to its high carcinogen potential. The health risk assessment with CalTOX showed that risk mainly came from two exposure pathways: dermal uptake and ingestion. Only one zone was classified in the high risk level and rest of the zones did not exceed the acceptable health risk value (>10-E6) without requiring remediation actions. The environmental compartment that required main attention was the surface soil. [Received: September 22, 2009; Accepted: December 8, 2009]

CKow: A Dynamic Model for Chemical Transfer to Meat and Milk

The objective of this study is to increase the understanding and transparency of chemical biotransfer modeling into meat and milk and explicitly confront the uncertainties in exposure assessments of chemicals that require such estimates. In cumulative exposure assessments that include food pathways, much of the overall uncertainty is attributable to the estimation of transfer into biota and through food webs. Currently, the most commonly used meat and milk-biotransfer models date back two decades and, in spite of their widespread use in multimedia exposure models, few attempts have been made to advance or improve the outdated and highly uncertain K(ow) regressions used in these models. Furthermore, in the range of K(ow) where meat and milk become the dominant human exposure pathways, these models often provide unrealistic rates and do not properly reflect the transfer dynamics. To address these issues, we developed a dynamic three-compartment cow model (called CKow), distinguishing lactating and nonlactating cows. For chemicals without available overall removal rates in the cow, a correlation is derived from measured values reported in the literature to predict this parameter from K(ow). Results on carry over rates (COR) and biotransfer factors (BTF) demonstrate that a steady-state ratio between animal intake and meat concentrations is almost never reached. For meat, empirical data collected on short-term experiments need to be adjusted to provide estimates of average longer term behaviors. The performance of the new model in matching measurements is improved relative to existing models-thus reducing uncertainty. The CKow model is straightforward to apply at steady state for milk and dynamically for realistic exposure durations for meat COR.

Distribution and health risk assessment of organochlorine pesticides (OCPs) in industrial site soils: A case study of urban renewal in Beijing, China

A ffield survey was conducted in a contaminated industrial site of southern Beijing, China to investigate the contents and distribution of the organochlorine pesticides (α-, β-, γ-, δ-HCH, p,p′-DDT, p,p′-DDE, p,p′-DDD and o,p′-DDT) in the proffiles of soil, and a health risk assessment was carried out with CalTOX multimedia exposure model. Results showed that mean concentrations of total hexachlorocyclohexane isomers (HCHs) and total dichlorodiphenyltrichloroethane isomers (DDXs) in soils were in the range of 13.20–148.71 mg/kg, and 3.02–67.43 mg/kg, respectively. Organochlorine pesticides (OCPs) content peaked in the surface and declined in soil proffile with depth. The amounts of HCHs in three proffiles of soil were larger than DDXs. Composition analysis indicated that there was a trend of degradation of OCPs in the site, but the mean of HCHs and DDXs concentration were over the state warning standard limit (HCHs, 0.50 mg/kg; DDXs, 0.50 mg/kg). According to current land use development, health risk assessment with CalTOX and Monte Carlo analysis showed that health risks mainly came from two exposure pathways: dermal uptake and inhalation, and the total risk values all exceeded the general acceptable health risk value (10 −6). The sensitivity analysis indicated that ffive parameters signifficantly contributed to total risk.

Multicompartmental fate of persistent substances

Modelling of the fate of environmental chemicals can be done by relatively simple multi-media box models or using complex atmospheric transport models. It was the aim of this work to compare the results obtained for both types of models using a small set of non-ionic and non-polar or moderately polar organic chemicals, known to be distributed over long distances. Predictions of multimedia exposure models of different types, namely three multimedia mass-balance box models (MBMs), two in the steady state and one in the non-steady state mode, and one non-steady state multicompartment chemistry-atmospheric transport model (MCTM), are compared for the first time. The models used are SimpleBox, Chemrange, the MPI-MBM and the MPI-MCTM. The target parameters addressed are compartmental distributions (i.e. mass fractions in the compartments), overall environmental residence time (i.e. overall persistence and eventually including other final sinks, such as loss to the deep sea) and a measure for the long-range transport potential. These are derived for atrazine, benz-[a]-pyrene, DDT, alpha and gamma-hexachlorocyclohexane, methyl parathion and various modes of substance entry into the model world. Compartmental distributions in steady state were compared. Steady state needed 2-10 years to be established in the MCTM. The highest fraction of the substances in air is predicted by the MCTM. Accordingly, the other models predict longer substance persistence in most cases. The results suggest that temperature affects the compartmental distribution more in the box models, while it is only one among many climate factors acting in the transport model. The representation of final sinks in the models, e.g. burial in the sediment, is key for model-based compartmental distribution and persistence predictions. There is a tendency of MBMs to overestimate substance sinks in air and to underestimate atmospheric transport velocity as a consequence of the neglection of the temporal and spatial variabilities of these parameters. Therefore, the long-range transport potential in air derived from MCTM simulations exceeds the one from Chemrange in most cases and least for substances which undergo slow degradation in air. MBMs should be improved such as to ascertain that the significance of the atmosphere for the multicompartmental cycling is not systematically underestimated. Both types of models should be improved such as to cover degradation in air in the particle-bound state and transport via ocean currents. A detailed understanding of the deviations observed in this work and elsewhere should be gained and multimedia fate box models could then be 'tuned in' to match better the results of comprehensive multicompartmental transport models.

Influence of Distributional Shape of Substance Parameters on Exposure Model Output

Uncertainty of environmental concentrations is calculated with the regional multimedia exposure model of EUSES 1.0 by considering probability input distributions for aqueous solubility, vapor pressure, and octanol-water partition coefficient, K(ow). Only reliable experimentally determined data are selected from available literature for eight reference chemicals representing a wide substance property spectrum. Monte Carlo simulations are performed with uniform, triangular, and log-normal input distributions to assess the influence of the choice of input distribution type on the predicted concentration distributions. The impact of input distribution shapes on output variance exceeds the effect on the output mean by one order of magnitude. Both are affected by influence and uncertainty (i.e., variance) of the input variable as well. Distributional shape has no influence when the sensitivity function of the respective parameter is perfectly linear. For nonlinear relationships, overlap of probability mass of input distribution with influential ranges of the parameter space is important. Differences in computed output distribution are greatest when input distributions differ in the most influential parameter range.

Human exposure and health risk of α-, β-, γ- and δ-hexachlorocyclohexane (HCHs) in Tianjin, China

The dynamic exposures to HCHs of individuals born between the years 1913 and 1993 in Tianjin have been simulated by connecting a fugacity model (IV) with a multimedia exposure model. Ingestion is the most important pathway for human beings to take up HCHs, and concentrations in the human body correlate with body weight changes. Accumulations of HCHs were derived assuming that the degradation in human body behaved linearly. The health risk of exposure to HCHs was measured using cancer risk and loss of life expectancy (LLE), and LLE was modified from its original definition to incorporate a dynamic calculation that takes variances in exposure into account. Monte-Carlo simulations were run to analyze the uncertainties of the model.

Public health benefits of compliance with current E.U. emissions standards for municipal waste incinerators: A health risk assessment with the CalTox multimedia exposure model

The Angers municipal solid waste incineration plant, in operation since 1974, was upgraded in 2000 to comply with new European standards. This article discusses the risks associated with past and present emissions from the incinerator and its nearby furnace. Emissions of SO 2, HCl, particulate matter, lead, mercury, cadmium and dioxins were studied. We characterised the risks associated with exposure via inhalation and ingestion of locally grown products, before and after the upgrade. Emissions were estimated from regulatory measurements, and ambient air concentrations estimated with a Gaussian dispersion model. The CalTox multimedia model was used to calculate concentrations in the food chain. Food intake rates came from a nationwide survey. Inhalation exposure to respiratory irritants produced a hazard ratio less than 1 in all scenarios, except for SO 2 in the immediate neighbourhood of the incinerator, before the change in furnace fuel and in case of high-pressure weather conditions. The individual excess risk of cancer was less than 10 −6 and the hazard ratios for metals were less than 1. Before compliance, the average dioxin exposure attributable to the incinerator accounted for roughly one quarter of the average total exposure from traffic and other combustion activities. Although the corresponding hazard ratio was less than 1, the individual lifetime excess risk, assuming no change in emissions, was 2·10 −4. After compliance, all hazard ratios and future individual lifetime excess risks appear minimal. These results are consistent with environmental data and other studies, but many uncertainties remain, such as intermedia transfer coefficients for dioxins. Nevertheless compliance has vastly reduced the probability of health effects.

Recent developments in broadly applicable structure-biodegradability relationships.

Biodegradation is one of the most important processes influencing concentration of a chemical substance after its release to the environment. It is the main process for removal of many chemicals from the environment and therefore is an important factor in risk assessments. This article reviews available methods and models for predicting biodegradability of organic chemicals from structure. The first section of the article briefly discusses current needs for biodegradability estimation methods related to new and existing chemicals and in the context of multimedia exposure models. Following sections include biodegradation test methods and endpoints used in modeling, with special attention given to the Japanese Ministry of International Trade and Industry test; a primer on modeling, describing the various approaches that have been used in the structure/biodegradability relationship work, and contrasting statistical and mechanistic approaches; and recent developments in structure/biodegradability relationships, divided into group contribution, chemometric, and artificial intelligence approaches.

The Precision of QSAR Methods For Estimating Intermedia Transfer Factors in Exposure Assessments

Abstract Dose assessments based on multimedia exposure models require intermedia-transfer factors (ITFs) as input. These factors relate contaminant concentrations in an environmental medium (the source medium such as air. water, or soil for which measurements are available) to the exposure medium (personal air, tap water, and food products) with which humans have contact. In this paper, I use QSAR as applied to partition coefficients between soil and plants, air and plants, and between animal diet and lipid tissues as case studies for characterizing the precision of ITF estimations. These partition coefficients form the basis of total dose models required for realistic exposure/risk assessments. The quantitative relationship between ITFs and chemical properties are developed along with the estimation errors associated with these relationships. Many of these correlations have large estimation errors that limit their reliability as applied in risk assessment. I examine factors that contribute to these estim...

PCDD/PCDF multimedia exposure analysis for the Canadian population: Detailed exposure estimation

Ontario has participated with the Canadian government in developing the basis for national multimedia gidelines for PCDD and PCDF. This paper provides a detailed description of the multimedia exposure model used to estimate exposure of Canadians to ambient levels of PCDD and PCDF in air, water, soil, food and consumer products.