Soil Ingestion Rates Research Articles

How much soil do cattle ingest? A review

Beef and dairy cattle commonly ingest soil when consuming forage-based diets in paddock feeding situations. However, the extent of this soil intake is poorly understood in the Australian environment and under Australian grazing systems. Therefore, the aim of the current literature review was to examine soil ingestion in cattle and the factors that affect ingestion. We found 11 studies containing soil-ingestion data, based in England, France, New Zealand and USA but none from Australia. A wide range in soil ingestion rates was reported and intake varied considerably with season, forage-pasture type, pasture-on-offer, stocking rate and grazing conditions. Generally, soil ingestion was lower in beef cattle than in dairy cattle. We considered the differences in reported levels, variables around those differences, and reliability of methodology used, and compared results with existing international guidelines. For Australian applications, we deduced and recommended that 0.5 kg/head.day is used until field-based research is conducted in Australia which might provide a more specific value for Australian conditions. Our review will inform future livestock management, particularly on contaminated agricultural land.

Meta-analysis of soil and dust ingestion studies

The ingestion of soil and dust by children and adults is a potential source of exposure to environmental contaminants. To advance beyond the simple averaging of estimates used in the U.S. EPA's Exposure Factors Handbook (EFH), we describe a novel meta-analysis of all available studies that provided soil or dust ingestion estimates for children or adults conducted in the United States and Canada. Using meta-analytic techniques, we estimate the mean total soil plus dust ingestion rates and confidence intervals (CIs) for eleven age groups (0 - <1 month (m), 1 - <3 m, 3 - <6 m, 6 - <12 m, 1 - <2 years (y), 2 - <3 y, 3 - <6 y, 6 - <11 y, 11 - <16 y, 16 - <21 y, and 21+ y). These age groups were selected for consistency with the EFH update to Chapter 5 and the U.S. EPA's Age Grouping Guidance. For each age group, we calculated best estimates for the three main types of ingestion studies: tracer studies based on the aluminum tracer, biokinetic studies, and activity pattern (modeling) studies, as well as overall estimates for all three study types combined. Our meta-analysis combined study estimates using the alternative statistical approaches of the fixed effect method (inverse variance method, “I–V”) and two random effects methods, DerSimonian and Laird's method of moments (“DSL”) and the restricted maximum likelihood method (“MIXED”). For each approach, the mean total soil plus dust ingestion rate estimates for each study type generally aligned well with the EFH, ranging from 36 to 68 mg/day for infants, 56–72 mg/day for young children, and 12–32 mg/day for adolescents and adults. When all three study types were combined, the upper bounds of the 95% CI were generally the lowest for the I–V method and the highest for the MIXED method. The estimates produced here can be used for stochastic risk assessments and provide a better estimate of soil and dust ingestion rates across age groups.

Quantifying earthworm soil ingestion from changes in vertical bulk density profiles

Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were Aporrectodea trapezoides, Aporrectodea tuberculata, Aporrectodea rosea, Lumbricus rubellus and Lumbricus Terrestris (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

Advancing Methodologies Used in Trace Element-Based Mass Balance Studies to Separately Estimate Soil and Dust Ingestion Rates for Children

Historically, soil ingestion rate estimates were based on trace element-based mass balance (MB) study results. These were used in assessing exposures and health risks for children residing in Superfund or chemically contaminated communities. However, soil and dust can have considerable differences with respect to their sources, chemical, physical, and toxicological characteristics. Unfortunately, the MB approach is incapable of disentangling dust ingestion rates from soil ingestion rates. Alternative methods, such as activity pattern and biokinetic modeling techniques, have also been used to predict soil and dust ingestion rates. The results from these studies differed from those obtained from the MB studies. This research evaluated the MB methodology and formulated a physical model which characterized the environmental and behavioral determinants of soil and dust ingestion exposures by children. This new approach explicitly separates outdoor soil exposures from the indoor tracked-in soil portion of the dust and total dust exposures by utilizing information from five key MB studies along with new information derived from the SHEDS-Soil/Dust time-activity pattern-based modeling runs. Application of this new hybrid methodology showed that the predicted mean soil ingestion rates are 30%-70% less than the “total soil” ingestion rates obtained from the selected MB studies. In contrast, most of the predicted dust ingestion rate estimates were typically greater than the predicted soil ingestion rates. Moreover, the predicted total soil plus dust ingestion rates were found to be mostly higher (by ≤ 60%) than the MB-based “total soil” ingestion rates. Except for one study these results were higher than the results produced by the stand-alone SHEDS-Soil/Dust model runs. Across the MB studies analyzed, predicted outdoor soil ingestion rate contributions to “total soil” ingestion rates varied between 29% and 70% while the tracked-in soil portion of the indoor dust ingestion rates varied between 30% and 71%.

Model-based predictions of soil and dust ingestion rates for U.S. adults using the stochastic human exposure and dose simulation soil and dust model

BackgroundAdults can be exposed to chemicals through incidental ingestion of soil and dust, either through hobbies, occupations, or behaviors that increase contact with soil or dust (e.g., cleaning or renovating). However, few data describing these ingestion rates are available. ObjectiveOur objective was to use the Stochastic Human Exposure and Dose Simulation Soil and Dust (SHEDS-Soil/Dust) model to estimate distributions of soil and dust ingestion rates for adults (≥21 years old) with varying degrees of soil and dust contact. MethodsWe parameterized SHEDS-Soil/Dust to estimate soil and dust ingestion rates for several categories of adults: adults in the general population; adults with moderate (higher) soil exposure (represented by hobbyists, such as gardeners, with increased soil contact); adults with high soil exposure (represented by occupationally exposed individuals, such as landscapers); and individuals who have high dust exposure (e.g., are in contact with very dusty indoor environments). ResultsTotal soil plus dust ingestion for adults in the general population was 7 mg/day. Hobbyists or adults with moderate soil exposure averaged 33 mg/day and occupationally exposed individuals averaged 123 mg/day. Total soil plus dust ingestion for adults in the high dust exposure scenario was 25 mg/day. Results were driven by time spent in contact with soil and, thus, warmer seasons (e.g., summer) were associated with higher ingestion rates than colder seasons (e.g., winter). SignificanceThese results provide modeled estimates of soil and dust ingestion rates for adults for use in decision making using real-world exposure considerations. These modeled estimates suggest that soil and dust ingestion is a potential concern for adults who spend a higher amount of time interacting with either soil or dusty environments. Impact statementThe parameterization of real-world scenarios within the application of SHEDS-Soil/Dust model to predict soil and dust ingestion rates for adults provides estimates of soil and dust ingestion rates useful for refining population-based risk assessments. These data illuminate drivers of exposure useful for both risk management decisions and designing future studies to improve existing tracer methodologies.

Estimation of Children's Soil and Dust Ingestion Rates and Health Risk at E-Waste Dismantling Area.

Due to environmental health concerns, exposure to heavy metals and related adverse effects in electronic waste (e-waste) dismantling areas have attracted considerable interest in the recent years. However, little information is available about the Soil/Dust Ingestion Rates (SIR) of heavy metals for children living in such sites. This study estimated the soil ingestion of 66 children from e-waste disassembly areas by collecting and analyzing selected tracer elements in matched samples of their consumed food, feces, and urine, as well as soil samples from their play areas. The concentrations of tracer elements (including Al, Ba, Ce, Mn, Sc, Ti, Y, and V) in these samples were analyzed. The SIR was estimated to be 148.3 mg/day (median) and 383.3 mg/day (95th percentile) based on the Best Tracer Method (BTM). These values are somewhat higher than those observed in America, Canada, and other parts of China. Health risk assessments showed that Cr presented the greatest carcinogenic risk, at more than 10−6 in this typical polluted area, while As was second. These findings provide important insights into the exposure risks of heavy metals in e-waste dismantling sites and emphasize the health risk caused by Cr and As.

Model based prediction of age-specific soil and dust ingestion rates for children

BackgroundSoil and dust ingestion can be a primary route of environmental exposures. Studies have shown that young children are more vulnerable to incidental soil and dust ingestion. However, available data to develop soil and dust ingestion rates for some child-specific age groups are either lacking or uncertain.ObjectiveOur objective was to use the Stochastic Human Exposure and Dose Simulation Soil and Dust (SHEDS-Soil/Dust) model to estimate distributions of soil and dust ingestion rates for ten age ranges from infancy to late adolescents (birth to 21 years).MethodsWe developed approaches for modeling age groups previously not studied, including a new exposure scenario for infants to capture exposures to indoor dust via pacifier use and accounting for use of blankets that act as a barrier to soil and dust exposure.ResultsOverall mean soil and dust ingestion rates ranged from ~35 mg/day (infants, 0–<6 m) to ~60 mg/day (toddlers and young children, 6m–<11 yr) and were considerably lower (about 20 mg/day) for teenagers and late adolescents (16–<21 y). The pacifier use scenario contributed about 20 mg/day to the median dust ingestion rate for young infants. Except for the infant age groups, seasonal analysis showed that the modeled estimates of average summer mean daily total soil plus dust ingestion rates were about 50% higher than the values predicted for the winter months. Pacifier use factors and carpet dust loading values were drivers of exposure for infants and younger children. For older children, influential variables included carpet dust loading, soil adherence, and factors that capture the frequency and intensity of hand-to-mouth behaviors.SignificanceThese results provide modeled estimates of children’s soil and dust ingestion rates for use in decision making using real-world exposure considerations.Impact statementThe parameterization of scenarios to capture infant soil and dust ingestion and the application of SHEDS-Soil/Dust to a broader age range of children provides additional estimates of soil and dust ingestion rates that are useful in refining population-based risk assessments. These data illuminate drivers of exposure that are useful to both risk management applications and for designing future studies that improve upon existing tracer methodologies.

Potential driving forces and probabilistic health risks of heavy metal accumulation in the soils from an e-waste area, southeast China

The integrated analysis of the distribution characteristics, health risks, and source identification of heavy metals is crucial for formulating prevention and control strategies for soil contamination. In this study, the area around an abandoned electronic waste dismantling center in China was selected as the research area. The probabilistic health risks caused by heavy metals were evaluated by the Monte Carlo simulation. Random forest, partial least squares regression, and generalized linear models were utilized to predict heavy metal distributions and identify the potential driving factors affecting heavy metal accumulation in soil. The relationships of spatial variation between the heavy metal contents and environmental variables were further visualized. The results revealed that cadmium (Cd) and copper (Cu) were the primary soil pollutants in the study area and caused high ecological risks. The probabilistic health risk assessment indicated that the non-carcinogenic and carcinogenic risks for all populations were acceptable. However, children are more susceptible to heavy metal soil contamination than adults. The sensitivity analyses indicated that the total contents of soil heavy metals and soil ingestion rate were the dominant factors affecting human health. The random forest model, with R2 values of 0.41, 0.65, 0.57, 0.71, and 0.58 for Cd, Cu, Ni, Zn, and Pb, respectively, predicted the heavy metal concentrations better than the other two models. The distance to the nearest industrial enterprise, industrial output, and agricultural chemical input were the main factors affecting Cd, Cu, Zn, and Pb accumulations in the soil, and soil pH and soil parent material were the primary factors influencing Ni accumulation in the soil. The visualization results of the geographically weighted regression model showed a significant relationship between soil heavy metal contents and industrial activity level. This study could be utilized as a reference for policymakers to formulate prevention and control strategies for heavy metal pollution in agricultural areas.

Antimony, beryllium, cobalt, and vanadium in urban park soils in Beijing: Machine learning-based source identification and health risk-based soil environmental criteria

The pollution situation of antimony (Sb), beryllium (Be), cobalt (Co), and vanadium (V) is poorly understood, although they are widely used in daily life and production processes. Moreover, threshold levels (“soil environmental criteria”, SEC) for these pollutants are lacking in China, which impedes effective soil quality management. This study explored pollution characteristics for park soils in urban area of Beijing, China at first. Then multivariate statistical analysis and machine learning model were used to identify the main sources of pollutants. Additionally, probabilistic health risk and SEC were studied to assess the risks of pollutants and manage soil pollutants. The results revealed that the overall pollution levels of Be, Co, Sb, and V were low, but Be and Sb were enriched to varying degrees. Source apportionment showed that Sb (85.5%) was mainly derived from fuel combustion and industrial legacy, Co (66.7%) and V (82.5%) from natural processes, and Be from the natural background (39.3%) and anthropogenic sources (53.8%). Risk assessment indicated that the pollutants' carcinogenic and noncarcinogenic risks were negligible. Exposure frequency and soil ingestion rate were the most important parameters affecting health risks. The SEC of Be, Co, Sb, and V were 31, 39.7, 41.3, and 348 mg/kg, respectively, all of which are higher than the corresponding soil quality standards in China, indicating that current soil quality standards may be too conservative for urban park land. This study provides a reference for the management of soil pollutants in Beijing's urban parks, and the formulation of soil environmental quality standards.

Health Risk Assessment of Metals via Multi-Source Oral Exposure for Children Living in Areas with Intense Electronic Manufacturing Activities.

Oral ingestion is the predominant pathway of metal(loid)s exposure. In this study, the health risks of typical metal(loid)s (including Mn, As, Cr, Cd, and Pb) via multi-source, oral pathways for children aged 3–12 years, living in an area of China dominated by the electronic manufacturing industry, were studied based on the field sampling of duplicated diet, soil, and drinking water. Child-specific ingestion parameters were measured (except the soil ingestion rates, which were from a previous study of the same population), and a Monte Carlo method was applied to determine the uncertainty of the risk assessment. It was observed that children living in such environments were at risk of metal(loid)s exposure, with the accumulative carcinogenic risk exceeding the maximum acceptable level. Food intake was identified to be the primary exposure pathway. Moreover, Pb and Cr were the major risk elements to local children’s health. Compared with primary school students, kindergarten children experienced a higher risk. This study highlights that high attention should be paid to children living in suburban areas dominated by the electronic manufacturing industry, and that priority should be given to studies on metal(loid)s exposure deriving from different types of food and their corresponding bioavailability, in order to further discern the precise risk sources to protect children’s health.

Estimation of Soil and Dust Ingestion Rates from the Stochastic Human Exposure and Dose Simulation Soil and Dust Model for Children in Taiwan.

This study focuses on estimating the probabilistic soil and dust ingestion rates for children under 3 years old by the Stochastic Human Exposure and Dose Simulation Soil and Dust (SHEDS-S/D) model developed by the U.S. Environmental Protection Agency. The health risk of children's exposure to heavy metals through soil and dust ingestion and dermal absorption was then assessed in three exposure scenarios. In the exposure scenario of direct contact with soil, the average soil and dust ingestion rates for children aged 24 to 36 months were 90.7 and 29.8 mg day-1 in the sand and clay groups, respectively. Hand-to-mouth soil ingestion was identified as the main contributor to soil and dust ingestion rates, followed by hand-to-mouth dust ingestion and object-to-mouth dust ingestion. The soil-to-skin adherence factor was the most influential factor increasing the soil and dust ingestion rate based on a sensitivity analysis in the SHEDS-S/D model. Furthermore, the modeled soil and dust ingestion rates based on the SHEDS-S/D model were coincident with results calculated by the tracer element method. Our estimates highlight the soil ingestion rate as the key parameter increasing the risk for children, while a higher frequency of hand washing could potentially reduce the risk.

Key considerations for assessing soil ingestion exposures among agricultural workers

BackgroundSoil ingestion is a critical, yet poorly characterized route of exposure to contaminants, particularly for agricultural workers who have frequent, direct contact with soil.ObjectiveThis qualitative investigation aims to identify and characterize key considerations for translating agricultural workers’ soil ingestion experiences into recommendations to improve traditional exposure science tools for estimating soil ingestion.MethodsWe conducted qualitative in-depth interviews with 16 fruit and vegetable growers in Maryland to characterize their behaviors and concerns regarding soil contact in order to characterize the nature of soil ingestion in the agricultural context.ResultsWe identified and discussed four emergent themes: (1) variability in growers’ descriptions of soil and dust, (2) variability in growers’ soil contact, (3) growers’ concerns regarding soil contact, (4) growers’ practices to modify soil contact. We also identified environmental and behavioral factors and six specific agricultural tasks that may impact soil ingestion rates.SignificanceOur investigation fills an important gap in occupational exposure science methodology by providing four key considerations that should be integrated into indirect measurement tools for estimating soil ingestion rates in the agricultural context. Specifically, a task-based framework may provide a structure for future investigations of soil contact that may be useful in other populations.

Estimating Children's Soil and Dust Ingestion Rates for Exposure Science (EPA)

Estimating Children's Soil and Dust Ingestion Rates for Exposure Science (EPA)

Heavy metal pollution and health risk assessment of soils from open dumps in the Metropolitan Area of Buenos Aires, Argentina.

We assessed heavy metal pollution and potential health risk by ingestion of soil in six open dumps in the Metropolitan Area of Buenos Aires (MABA), Argentina. For the determination of Cd, Cu, Ni, Pb, Zn, Hg, and Cr, soil samples were taken from the first 10cm using sampling grids installed between the boundaries of the waste final disposal sites and the beginning of the urban area. Soil samples were considered contaminated if at least one metal exceeded the maximum levels established by the Argentine regulation. Potential health risk by soil ingestion was calculated using deterministic analysis for both adults and children and stochastic analysis only for children. In 39.8% (N = 171) of the soil samples, the concentration of at least one metal was above the guide levels. Concentrations of Pb, Cu, and Zn exceeded maximum permissible values in all open dumps. Except for Hg, heavy metal concentrations differed significantly among open dumps. Hazard indexes > 1 were obtained for the children's population using both deterministic and stochastic models. The most sensitive variables in the stochastic model were exposure frequency and soil ingestion rate, together explaining 70% of the variation in the forecasts. The calculated risks were highly dependent on Pb concentrations. The determination of blood lead concentration in children and the assessment of other exposure routes are needed in areas of open dump influence in MABA.

Development of General Exposure Factors for Risk Assessment in Korean Children.

There has been an increasing need for the risk assessment of external environmental hazards in children because they are more sensitive to hazardous chemical exposure than adults. Therefore, the development of general exposure factors is required for appropriate risk assessment in Korean children. This study aimed to determine the general exposure factors among Korean children aged ≤18 years. We developed the recommended exposure factors across five categories: physiological variables, inhalation rates, food and drinking water intake, time–activity patterns, and soil and dust ingestion. National databases were used, and direct measurements and questionnaire surveys of representative samples were performed to calculate the inhalation rate, water intake, and soil ingestion rate. With regard to the time–activity patterns, the daily inhalation rates ranged from 9.49 m3/day for children aged 0–2 years to 14.98 m3/day for those aged 16–18 years. This study found that Korean children spent an average of 22.64 h indoors, 0.63 h outdoors, and 0.73 h in-transit on weekdays. The general exposure factors of Korean children were studied for the first time, and these results could be used to assess children’s exposure and risk. They also suggest the differences compared with the results of international results.

Comprehensive comparison of probabilistic health risks of soil heavy metals in China’s mining areas

To assess the health risks caused by soil heavy metal in China’s mining areas, concentration data for eight heavy metals in 77 mines were collected from previous literature. Monte Carlo simulation was used to analyze the corresponding carcinogenic risks and noncarcinogenic risks, and sensitivity analysis was carried out for each parameter. The results showed that among the different types of mining areas, multi-metal mines have the highest risk of carcinogenesis, followed by tungsten and antimony mines. Their carcinogenic risk values are all greater than 10−4, which is unacceptable. Pb is a heavy metal with highest noncarcinogenic risk. The log-transformed value is 3.2, which is much larger than the threshold of 0; Pb is followed by As and Hg. Therefore, Pb, As, and Hg are the heavy metals that should be controlled preferentially in polluted mining areas. Sensitivity analysis showed that the soil ingestion rate, exposure frequency, and pollutant concentration level are the factors that have the greatest impacts on health risks. More attention should be paid to these factors when addressing heavy metal pollution in mining areas. In addition, for the surveyed mines, children had a greater health risk than adults, so children should be given extra attention.

Soil intake in ruminants grazing on heavy-metal contaminated shooting ranges

Shooting ranges contain copper and lead from spent ammunition, this contamination can represent a risk for ruminants grazing there. The present study investigated the intake of copper and lead by sheep and cattle grazing on shooting ranges. Three factors are important for the ingested dose of metals: soil ingestion rate, accumulation of the metals in plants and grazing behavior. Up to 3700 mg Pb/kg dry weight (dw) and 1654 mg Cu/kg (dw) was found in soil and up to 52 mg Pb/kg (dw) and 35 mg Cu/kg (dw) was found in grass. The limit for sensitive land use set by the Norwegian Environment Agency is 60 mg Pb/kg and 100 mg Cu/kg, and the EU limit in fodder is 33.6 mg Pb/kg (dw). Soil ingestion was found by using titanium as a tracer, as titanium is abundant in soil, but not taken up in plants or animals. Low soil ingestion rates (<2%) were found in all investigated areas, including three shooting ranges and one cultivated pasture. There was no correlation between the copper concentration in soil and grass, such a correlation was found for lead. The risk of copper and lead poisoning by ruminants on shooting ranges was assessed based on the copper and lead concentration in the soil and grass, the soil ingestion rate and the grazing behavior. The risk assessment concluded that the calculated dose of copper (chronic sheep: 0.07, cattle: 0.08, acute sheep: 0.7, cattle: 0.8, mg/kg, body weight (bw), day) and lead (chronic sheep: 0.12, cattle: 0.12, acute sheep: 1.2, cattle: 1.2, mg/kg, bw, day) ingested by ruminants was much lower than both the assumed chronic (Cu sheep: 0.26–0.35 cattle: 8, Pb sheep and cattle:6, mg/kg, bw, day) and acute toxic doses (Cu sheep: 20–100, Pb sheep and cattle: 600–800, mg/kg bw) for sheep and cattle.

Using Sheds-S/D Model to Estimate Soil and Dust Ingestion Rates for Adults

Soil and dust ingestion is the primary pathway for environmental exposure to some pollutants. As is the case with children, incidental soil and dust ingestion rates for adults are dependent on the ...

Assessment of intake of copper and lead by sheep grazing on a shooting range for small arms: a case study.

The Norwegian Armed Forces' shooting ranges contain contamination by metals such as lead (Pb) and copper (Cu) and are often used as grazing pastures for livestock. To determine whether the sheep were at risk from grazing at a shooting range in Nord-Trøndelag (the Leksdalen shooting field), a study was conducted wherein the aim was to determine the amount of soil the sheep were eating, the accumulation of Cu and Pb in the livers of lambs grazing on the shooting ranges, and the accumulation of Pb and Cu in the grass. The grazing behavior of the sheep was mapped using GPS tracking and wildlife cameras. Soil, grass, feces, and liver samples were collected. All the samples were analyzed for Pb, Cu, and molybdenum (Mo), and soil and feces were also analyzed for titanium (Ti). Mean concentrations in grass, soil, feces, and liver was 41-7189, 1.3-29, 4-5, and 0.3mg/kg Pb, respectively, and 42-580, 4.2-11.9, 19-23, and 273mg/kg Cu, respectively. The soil ingestion rate was calculated using Ti in feces and soil. From these results, the theoretical dose of Cu and Pb ingested by grazing sheep was calculated. The soil ingestion rate was found to be 0.1-0.4%, significantly lower than the soil ingestion rate of 5-30% usually used for sheep. Little or no accumulation of Cu and Pb in the grass was found. There was no difference between the metal concentrations in the washed and unwashed grass. According to the calculated dose, the sheep were at little or no risk of acute or chronic Pb and Cu poisoning from grazing on the Leksdalen shooting range. The analysis of liver samples showed that lambs grazing on the shooting range did not have higher levels of Cu or Pb than lambs grazing elsewhere. None of the lambs had concentrations of Cu or Pb in their livers indicating poisoning.

A soil ingestion pilot study for teenage children in China

Soil ingestion by people is an important route of exposure to environmental contaminants. Studies on soil ingestion using tracer mass-balance method are mainly for young children and adults, scarcely for teenagers. In such case, the soil ingestion rate for teenagers recommended by regulators is generally identical to that of adults based on one activity pattern modeling study. However, teenagers are expected to have different soil ingestion exposure via ingestion pathway due to different activity patterns and exposure scenarios. We conducted a pilot study on soil ingestion in 30 teenage children aged 12.0–16.5 years from Hubei Province of China, using the best tracer method, with the results compared with previous soil ingestion studies. The estimated mean and median soil ingestion rates for teenagers in this study based on the best five tracers (Al, Ce, Sc, V, and Y) were 45.2 mg d−1 and 44.8 mg d−1 respectively, with the 95% confidence interval of the mean value ranging from 28.0 mg d−1 to 50.9 mg d−1. These soil ingestion rate estimates were slightly higher than the recommended values for adults by U.S. EPA, but lower than those for Chinese younger children observed in the other similar study. The result in this study is important to access the health risk resulting from exposure to toxic substances in soil via direct soil ingestion pathway by teenagers in China as well as other countries.