Human Exposure Factors Research Articles

An innovative risk evaluation method on soil pathogens in urban-rural ecosystem

The presence and reproduction of pathogens in soil environment have significant negative impacts on soil security and human health in urban-rural ecosystem. Rapid urbanization has dramatically changed the land use, soil ecosystems, and the presence of pathogens in soil environment, however, the risk associated with soil pathogens remains unknown. Identifying the potential risk of pathogens in soils in urban-rural ecosystem has become an urgent issue. In this study, we established a risk evaluation method for soil pathogens based on analytic hierarchy process and entropy methods to quantitatively estimate the potential risk of soil pathogens to children and adults in urban-rural ecosystem. The abundance and species number of soil pathogens, network structure of soil microbial community, and human exposure factors were considered with 12 indicators to establish the risk evaluation system. The results revealed that 19 potential pathogenic bacteria were detected in soils within a typical urban-rural ecosystem. Substantial differences were observed in both abundance and species of soil pathogens as well as network structure of soil microbial community from urban to rural areas. Urban areas exhibited relatively lower levels of soil pathogenic abundance, but the microbial network was considerably unstable. Rural areas supported relatively higher levels of soil pathogenic abundance and stable microbial networks. Notably, peri-urban areas showed relatively unstable microbial networks alongside higher levels of soil pathogenic abundance compared to other areas. The risk evaluation of soil pathogens for both adults and children showed that peri-urban areas presented the highest potential risk, with children being more susceptible than adults to threats posed by soil pathogens in both urban and peri-urban areas. The established evaluation system provides an innovative approach for quantifying risk of soil pathogens at regional scale and can be used as a reference for preventing soil pathogens contamination and enhancing soil health in areas with intense human activities.

Combining data from heterogeneous surveys for aggregate exposure: Application to children exposure to lead in France

To assess human health risks related to the environment, it is necessary to aggregate exposure from multiple sources. The objective of this paper was to propose a relevant approach to combine data from heterogeneous populations and methodologies. Five different methods based on Monte-Carlo simulations were tested and compared. Differences were: taking into account or not stratification variable, timeline to assign exposure factors and concentration and way to account for concentration correlations. The methods were applied to estimate lead exposure from food, dust, soil, air, and tap water or French children aged between six months and three years old.Comparing results’ uncertainty, it is recommended to 1) select a reference population representative of the target population, 2) select stratification variables to combine surveys, and 3) simulate a new population by randomly sampling individuals in the reference population and simultaneously assigning human exposure factors and environmental concentrations from other surveys in integrating correlations (MC1S). No difference was observed when taking into account correlations using vectors of determinist data from one survey or rank of correlations with the Iman-Conover method. Regardless the methods used to combine data, dust was the main exposure source, followed by soil and in a less extent by food. Exposures from air and tap water were found to be insignificant for most children.

How are Humans Exposed to Organic Chemicals Released to Indoor Air?

Humans are exposed to organic chemicals released to indoor air through near-field exposure routes such as air inhalation and nondietary dust ingestion as well as far-field exposure routes such as consumption of food. Here, we explore the relative importance of near- and far-field exposure routes and its variability between chemicals, age groups, and subpopulations, by modeling aggregate human exposure to indoor-released chemicals with diverse partitioning behavior and degradability. Our model results indicate that if chemicals are assumed to be perfectly persistent, dietary and nondietary ingestion dominates human exposure to hydrophobic chemicals of relatively low volatility (with an octanol-air partition coefficient KOA > 106.5 and an octanol-water partition coefficient KOW < 1011), whereas inhalation of indoor air dominates human exposure to volatile chemicals. Other exposure routes, for example, dermal absorption and drinking water, make a relatively small contribution to human exposure. Reduced chemical persistence in environmental media and biota lowers the contribution of dietary ingestion. For most chemicals other than those with a KOA between 109 and 1012 and a KOW between 106 and 109 (e.g., polybrominated diphenyl ethers), the relative importance of near- and far-field exposure routes is primarily governed by chemical partitioning and degradability rather than age- and population-dependent human exposure factors.

Pollution characteristics of ambient PM2.5–bound benzo[a]pyrene and its cancer risks in Beijing

The purpose of this study was to reveal the pollution characteristics of ambient PM2.5–bound benzo[a]pyrene (B[a]P) in Beijing and to assess the lifetime cancer risk from respiratory pathway exposure. The average daily dose was evaluated by the annual concentrations of ambient PM2.5–bound B[a]P, combined with Chinese human exposure factors and the age sensitivity factors. The 70-year lifetime cancer risks of different groups were assessed by the exposure assessment and stochastic analysis method recommended by California Environmental Protection Agency. The groups were divided by age and gender. The results showed that the ambient PM2.5–bound B[a]P concentration during the cold season was 15.7 times greater than that during the warm season in Beijing. The annual average concentrations of PM2.5–bound B[a]P in outdoors and indoors were 1.67 ng/m3 and 1.04 ng/m3, respectively, which exceeded the limit of Chinese National Ambient Air Quality Standard. The cancer risks of PM2.5–bound B[a]P in males, females, and the general population were 9.085 × 10−6, 8.050 × 10−6, and 8.740 × 10−6, respectively. The cancer risk constituent ratios of ambient PM2.5–bound B[a]P in early life (≤16 years of age) for males, females, and the general population were 70.9%, 71.4%, and 71.3%, respectively. The males' cancer risk of PM2.5–bound B[a]P in Beijing was higher than that of the females. The early life cancer risk exposure to PM2.5–bound B[a]P should be paid more attention.

Human exposure factors as potential determinants of the heterogeneity in city-specific associations between PM2.5 and mortality.

Multi-city population-based epidemiological studies of short-term fine particulate matter (PM2.5) exposures and mortality have observed heterogeneity in risk estimates between cities. Factors affecting exposures, such as pollutant infiltration, which are not captured by central-site monitoring data, can differ between communities potentially explaining some of this heterogeneity. This analysis evaluates exposure factors as potential determinants of the heterogeneity in 312 core-based statistical areas (CBSA)-specific associations between PM2.5 and mortality using inverse variance weighted linear regression. Exposure factor variables were created based on data on housing characteristics, commuting patterns, heating fuel usage, and climatic factors from national surveys. When survey data were not available, air conditioning (AC) prevalence was predicted utilizing machine learning techniques. Across all CBSAs, there was a 0.95% (Interquartile range (IQR) of 2.25) increase in non-accidental mortality per 10 µg/m3 increase in PM2.5 and significant heterogeneity between CBSAs. CBSAs with larger homes, more heating degree days, a higher percentage of home heating with oil had significantly (p < 0.05) higher health effect estimates, while cities with more gas heating had significantly lower health effect estimates. While univariate models did not explain much of heterogeneity in health effect estimates (R2 < 1%), multivariate models began to explain some of the observed heterogeneity (R2 = 13%).

Using exposure prediction tools to link exposure and dosimetry for risk-based decisions: A case study with phthalates

A few different exposure prediction tools were evaluated for use in the new in vitro-based safety assessment paradigm using di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DnBP) as case compounds. Daily intake of each phthalate was estimated using both high-throughput (HT) prediction models such as the HT Stochastic Human Exposure and Dose Simulation model (SHEDS-HT) and the ExpoCast heuristic model and non-HT approaches based on chemical specific exposure estimations in the environment in conjunction with human exposure factors. Reverse dosimetry was performed using a published physiologically based pharmacokinetic (PBPK) model for phthalates and their metabolites to provide a comparison point. Daily intakes of DEHP and DnBP were estimated based on the urinary concentrations of their respective monoesters, mono-2-ethylhexyl phthalate (MEHP) and monobutyl phthalate (MnBP), reported in NHANES (2011–2012). The PBPK-reverse dosimetry estimated daily intakes at the 50th and 95th percentiles were 0.68 and 9.58 μg/kg/d and 0.089 and 0.68 μg/kg/d for DEHP and DnBP, respectively. For DEHP, the estimated median from PBPK-reverse dosimetry was about 3.6-fold higher than the ExpoCast estimate (0.68 and 0.18 μg/kg/d, respectively). For DnBP, the estimated median was similar to that predicted by ExpoCast (0.089 and 0.094 μg/kg/d, respectively). The SHEDS-HT prediction of DnBP intake from consumer product pathways alone was higher at 0.67 μg/kg/d. The PBPK-reverse dosimetry-estimated median intake of DEHP and DnBP was comparable to values previously reported for US populations. These comparisons provide insights into establishing criteria for selecting appropriate exposure prediction tools for use in an integrated modeling platform to link exposure to health effects.

Environmental and dietary exposure of young children to inorganic trace elements

Children are exposed to toxic metals and metalloids via their diet and environment. Our objective was to assess the aggregate chronic exposure of children aged 3–6years, living in France, to As, Cd, Cr, Cu, Mn, Pb, Sb, Sr, and V present in diet, tap water, air, soil and floor dust in the years 2007–2009. Dietary data came from the French Total Diet Study, while concentrations in residential tap water, soil and indoor floor dust came from the ‘Plomb-Habitat’ nationwide representative survey on children's lead exposure at home. Indoor air concentrations were assumed to be equal to outdoor air concentrations, which were retrieved from regulatory measurements networks. Human exposure factors were retrieved from literature. Data were combined with Monte Carlo simulations. Median exposures were 1.7, 0.3, 10.2, 34.1, 60.3, 0.7, 0.1, 44.3, 1.5 and 95th percentiles were 4.4, 0.5, 15.8, 61.3, 98.3, 2.5, 0.1, 111.1, 2.9μg/kgbw/d for As, Cd, Cr, Cu, Mn, Pb, Sb, Sr, and V respectively. Dietary exposures dominate aggregate exposures, with the notable exception of Pb - for which soils and indoor floor dust ingestion contribute most at the 95th percentile. The strengths of this study are that it aggregates exposures that are often estimated separately, and uses a large amount of representative data. This assessment is limited to main diet and residential exposure, and does not take into account the relative bioavailability of compounds. These results could be used to help target prevention strategies.

Exposure factors of cadmium for residents in an abandoned metal mine area in Korea

This study evaluated blood and urine cadmium (Cd) levels and human exposure factors for residents in an abandoned metal mine in Korea. We collected blood, urine, soil, water, and rice grain samples to analyze Cd concentrations and analyzed heavy metal concentration patterns in soil. We estimated the major exposure factor of Cd through non-carcinogenic risk assessment depending on exposure routes. The blood Cd concentration in the case group was 5.33 μg/L (geometric mean), significantly higher than that in the control group (1.63 μg/L, geometric mean). Urine Cd concentrations were also similar. The Cd concentrations in paddy soil (1.29 mg/kg) and rice grains (0.14 mg/kg) in the study area were higher than those in the control area (0.91 and 0.07 mg/kg, respectively). The analysis of heavy metal concentration in soil showed that the Cd levels in agricultural soil in the case group were attributable to the mine. The hazard quotient (HQ) of Cd by rice ingestion in the case group (1.25) was 2 times higher than that in the control group (0.6). We found that the HQ of rice ingestion contributed to more than 97 % of the total HQ, indicating that rice grains were the major exposure source. However, it is likely that the continuous intake of Cd-exposed crops led to chronic exposure among the residents in mine area.

Exposure factors resources: contrasting EPA’s Exposure Factors Handbook with international sources

Efforts to compile and standardize human exposure factors have resulted in the development of a variety of resources available to the scientific community. For example, the US Environmental Protection Agency (EPA) developed the Exposure Factors Handbook and Child-specific Exposure Factors Handbook to promote consistency among its various exposure-assessment activities. The US EPA handbooks are compilations of human exposure factors data, including anthropometric and sociocultural data (e.g., body weights, skin-surface areas, and life expectancy), behavioral data (e.g., non-dietary ingestion rates, activity/time use patterns, and consumer product use), factors that may be influenced by the physiological needs of the body, metabolic activity, and health and weight status (e.g., water and food intake, and inhalation rates), and other factors (e.g., building characteristics). Other countries have engaged in similar efforts to compile and standardize exposure factors for use in exposure and risk assessments. For example, the ExpoFacts database contains data for 30 European Union countries. Australia, Canada, Japan, Korea, and Taiwan have developed, or are developing, documents that provide exposure factors data relevant to their populations. The purpose of this paper is to provide an overview of some of the available exposure factors resources; to explore some of the similarities and differences between the US EPA Exposure Factors Handbook and selected other international resources, and to highlight data gaps and present some considerations for promoting consistency among these resources.

A characterization model with spatial and temporal resolution for life cycle impact assessment of photochemical precursors in the United States

Traditional life cycle impact assessment methodologies have used aggregated characterization factors, neglecting spatial and temporal variations in regional impacts like photochemical oxidant formation. This increases the uncertainty of the LCA results and diminishes the ease of decision-making. This study compares four common impact assessment methods, CML2001, Eco-indicator 99, TRACI, and EDIP2003, on their underlying models, spatial and temporal resolution, and the level at which photochemical oxidant impacts are calculated. A new characterization model is proposed that incorporates spatial and temporal differentiation. A photochemical air quality modeling system (CAMx-MM5-SMOKE) is used to simulate the process of formation, transformation, transport, and removal of photochemical pollutants. Monthly characterization factors for individual US states are calculated at three levels along the cause–effect chain, namely, fate level, human and ecosystem exposure level, and human effect level. The results indicate that a spatial variability of one order of magnitude and a temporal variability of two orders of magnitude exist in both the fate level and human exposure and effect level characterization factors for NOx. The summer time characterization factors for NOx are higher than the winter time factors. However, for anthropogenic VOC, the summer time factors are lower than the winter time in almost half of the states. This is due to the higher emission rates of biogenic VOCs in the summer. The ecosystem exposure factors for NOx and VOC do not follow a regular pattern and show a spatial variation of about three orders of magnitude. They do not show strong correlation with the human exposure factors. Sensitivity analysis has shown that the effect of meteorology and emission inputs is limited to a factor of three, which is several times smaller than the variation seen in the factors. Uncertainties are introduced in the characterization of photochemical precursors due to a failure to consider the spatial and temporal variations. Seasonal variations in photochemical activity influence the characterization factors more than the location of emissions. The human and ecosystem exposures occur through different mechanisms, and impacts calculated at the fate level based only on ozone concentration are not a good indicator for ecosystem impacts. Spatial and temporal differentiation account for fate and transport of the pollutant, and the exposure of and effect on the sensitive human population or ecosystem. Adequate resolution for seasonal and regional processes, like photochemical oxidant formation, is important to reduce the uncertainty in impact assessment and improve decision-making power. An emphasis on incorporating some form of spatial and temporal information within standard LCI databases and using adequately resolved characterization factors will greatly increase the fidelity of a standard LCA.

A Survey Methodology for Collecting Fish Consumption Data in Urban and Industrial Water Bodies (Part 1)

The potential human health risks associated with consuming fish containing hazardous substances are related to the frequency, duration, and magnitude of exposure. Because these risk factors are often site specific, they require site-specific data. In anticipation of performing a risk assessment of the lower 6 miles of the Passaic River in New Jersey (Study Area), a year-long creel/angler survey collected such site-specific data. The lower Passaic River is urbanized and industrialized, and its site conditions present unique survey design and sampling challenges. For example, the combined population of the municipalities surrounding the Study Area is nearly 330,000, but because the Study Area is tidal, state law does not require fishing licenses for anglers to fish or crab in the Study Area. The sampling challenges posed by the lack of licensing are exacerbated by the industrialization and lack of public access in the lower half of the Study Area. This article presents a survey methodology designed to overcome these challenges to provide data for accurately estimating the Study Area's angling population and the fish and crabs they catch, keep, and eat. In addition to addressing the challenges posed by an urban and industrial setting, the survey methodology also addresses the issues of coverage, avidity, and deterrence, issues necessary for collecting a representative sample of the Study Area's anglers. This article is a companion to two other articles. The first companion article describes the analytical methodology designed to process the data collected during the survey. The second presents, validates, and interprets the survey results relating to human exposure factors for the lower Passaic River.

Human Health Exposure Factor Estimates Based Upon A Creel/Angler Survey of the Lower Passaic River (Part 3)

The results of an analysis of site-specific creel and angler information collected for the lower 6 miles of the Passaic River in Newark, NJ (Study Area), demonstrate that performing a site-specific creel/angler survey was essential to capture the unique characteristics of the anglers using the Study Area. The results presented were developed using a unique methodology for calculating site-specific, human exposure estimates from data collected in this unique urban/industrial setting. The site-specific human exposure factors calculated and presented include (1) size of angler population and fish-consuming population, (2) annual fish consumption rate, (3) duration of anglers' fishing careers, (4) cooking methods for the fish consumed, and (5) demographic information. Sensitivity and validation analyses were performed, and results were found to be useful for performing a site-specific, human health risk assessment. It was also concluded that site-specific exposure factor values are preferable to less representative “default values.” The results of the analysis showed that the size of the angling population at the Study Area is estimated to range from 154 to 385 anglers, based on different methods of matching intercepts with anglers. Thirty-four anglers were estimated to have consumed fish; 37 people consumed fish from the river. The fish consumption rate for anglers using this area was best represented as 0.42 g/day for the central tendency and 1.8 g/day for the 95th percentile estimates. Anglers fishing at the river have relatively short fishing careers with a median of 0.9 yr, an average of 1.5 yr, and a 95th percentile of 4.8 yr. Consuming anglers tend to fry the fish they caught. The demographics of anglers who consume fish do not appear to differ substantially from those who do not, with no indication of a subsistence angling population.

A Statistical Method for Analyzing Data Collected by a Creel/Angler Survey (Part 2)

This article describes a unique analytical method employed to characterize angler activities on the lower 6-mile stretch of the Passaic River in New Jersey. The method used data collected by a creel/angler survey that was designed to capture the information necessary to calculate the exposure factors needed to characterize the fish consumption pathway for recreational anglers in a human health risk assessment for the river. The survey used two methods to address the challenges of conducting a creel/angler survey in an urban and industrial setting with limited river access. While unique, the analytical method described in this article is based upon accepted methods of interpreting survey data and basic laws of probability. This article was written as a companion to two other articles, also in this issue and cited here, of which one describes in detail the survey methodology designed for the lower Passaic River creel/angler survey to meet various challenges unique to conducting such a survey in urban and industrialized rivers, and the other presents, validates, and interprets the results of the lower Passaic River work relating to human exposure factors using the methodology described in this article.

Distributional Exposure Reference Values for Germany

P-641 Introduction: For the successful application of (probabilistic) exposure modelling, both sufficient data of good quality and guidance on their use are necessary. A German report on exposure factors dating from 1995 was partially made obsolete by recent studies and by requirements of probabilistic exposure modelling. The Xprob project aimed to evaluate recent data and methods of probabilistic exposure assessment, to derive distributions for exposure factors, and to provide guidelines on good practice of probabilistic exposure modelling. Methods: Comprehensive data and literature searches with focus on German sources were carried out, taking the 1995 report as a basis. These sources were analysed in a standardised way. A methodology for deriving distributions needed for probabilistic modelling was developed, based on a US EPA approach. This methodology was then applied to analyse the data sources. In addition, literature reviews were carried out to assess the quality of data sources and to fill data gaps. A database was developed and implemented for structured documentation and retrieval of the information gathered. Results: Based on more than 50 data and literature sources, recommendations concerning derived distributions of human exposure factors were made. They can also be used for point estimates. In the database RefXP developed by the project, the distributions and characteristics of the individual exposure factors are provided, structured by thematic areas. Information is given on data source, exposure factor, empirical and derived distribution, each stratified by age and gender. For some exposure factors (e.g. inhalation, soil ingestion), only data from literature were available. Various data gaps were identified. Discussion and Conclusions: The provision of distributions as well as point estimates for exposure factors in a uniformly structured database offers clear advantages. The distributions fit the empirical data. For filling remaining data gaps, the developed methodology should be used to evaluate recent studies hitherto inaccessible, as well as future studies. Derived principles of good practice will facilitate the application of probabilistic exposure modelling. Distribution based exposure reference values can contribute to a harmonisation of the assessment of environmental health risk assessment. Implementation into administrative policy, however, calls for additional support and practice-oriented developments. This project was funded by the German Federal Environmental Agency (UBA) under No. FKZ 20261218/02.

Health Risk Assessment of an Industrial Site Contaminated With Polycyclic Aromatic Hydrocarbons Using CalTOX, an Environmental Fate/Exposure Model

This paper presents the results of a risk assessment study made using CalTOX, a multimedia, multiple pathway risk assessment model. The case study is based on the Polycyclic Aromatic Hydrocarbon (PAH) soil contamination resulting from the activities of a natural gas power station over a period of 70 years. It describes model characteristics and input parameters such as physico-chemical properties, landscape description, and human exposure factors. Model simulations and risk estimations corresponding to different remedial scenarios in an industrial zone are also presented. These estimations were based on soil contamination by 16 PAHs in the root-zone and vadose-zone layer. Results show that adult exposure (workers) to contaminated soil will lead to a potential health risk of carcinogenic effects, and to no potential risk of non-carcinogenic effects. On the other hand, the addition of 10 cm of clean soil over the contaminated soil (mitigated scenario) decreases the lifetime cancer risk to an acceptable level. The sensitivity analysis showed that the half-life of benzo[a]pyrene in the root-zone soil is the most sensitive parameter and that it contributes significantly to the variability of the cancer risk estimation. In addition, the cancer risk level of the workers exposed to this substance, as estimated by CalTOX (point estimate) in the mitigated and unmitigated scenario, corresponds approximately to the 95th percentile value obtained by means of Monte-Carlo simulations. Finally, CalTOX has proven to be a valuable tool to predict and elaborate scenarios for the risk management of sites contaminated as a result of industrial activities.