Assessing Risk of Inorganic Arsenic in Drinking Water in the United States

Limitations of the current EPA risk assessment for inorganic arsenic in drinking water in the U.S. are discussed. An empirical approach is suggested that would sample survey the populations in regions with the highest arsenic levels in drinking water for signs of arsenicism, which has been much more prevalent and appeared much earlier in exposed populations than cancer (e.g., of the skin). Biomarkers of exposure, such as arsenic content in urine, nails, hair, and skin scales, may provide even earlier indications of subpopulations with excessive arsenic exposure and identify individuals at risk. Further study is needed to evaluate fully the potential for use of biomarkers, focusing on the accuracy and reliability of analytical methods, the utility of biomarkers as indicators of short-term and long-term exposure and as precursors to clinical signs of arsenicism, and the use of “normal” ranges of biomarkers for interpretation of field observations.     

Factors Controlling the Bioaccessibility of Arsenic(V) and Lead(II) in Soil

The relative oral bioaccessibility of labile Pb(II) and As(V) added to soils was investigated in a well-characterized soil using a physiologically based extraction test (PBET) to simulate metal solubility in a child's digestive system. The effect of soil and PBET (i.e., simulated stomach and small intestine) pH, soil metal concentration, soil to solution ratio, and soil-metal aging time were investigated. Arsenic bioaccessibility was relatively unaffected by a variation in simulated stomach and small intestine pH over the range 2 to 7 and soil pH over the range 4.5 to 9.4. In contrast, Pb(II) bioaccessibility was strongly dependent on both the simulated stomach, small intestine, and soil pH, showing enhanced sequestration and decreased bioaccessibility at higher pH values in all cases. Although the bioaccessibility of Pb(II) was constant over the concentration range of approximately 10 to 10,000?mg/kg, the As(V) bioaccessibility significantly increased over this concentration range. The bioaccessibility of both arsenic and lead increased as the soil-to-solution ratio decreased from 1:40 to 1:100. Additional lead sequestration was not observed during 6 months of soil aging, but As(V) bioaccessibility decreased significantly during this period.     

The Influence of Liquid to Soil Ratios on Arsenic and Lead Bioaccessibility in Reference and Field Soil

In vitro bioaccessibility testing is gaining popularity as a tool to estimate the oral bioavailability of contaminants in soil for human health risk assessment (HHRA). Bioaccessibility tests are used to measure the bioaccessible fraction of a contaminant in soil, which can then be used to estimate the bioavailable fraction. Inherent uncertainties are associated with bioaccessibility tests. Various test parameters need to be carefully considered in their development, including the liquid to soil (L/S) ratio employed. We used L/S ratios (v:wt) ranging from 25 ml:1 g to 1,000 ml:1 g in a modified relative bioaccessibility extraction procedure to investigate the effects on bioaccessibility of lead and arsenic in field and reference soils. General trends of increased percent bioaccessibility of lead and arsenic with increasing L/S ratio were observed in the reference soil. A similar positive relationship was observed for lead in the field soil; soluble arsenic concentrations were below the detection limit and data were insufficient to observe a trend. Percent bioaccessibility was significantly affected at each extreme of the L/S ratios tested (p < .05). Biological relevance, technical feasibility, and mathematical relationships with in vivo results should be considered when selecting an appropriate L/S ratio for bioaccessibility testing.     

Chromium,Copper, and Arsenic Concentrations in Soil Underneath CCA-Treated Wood Structures

Soils below nine structures (decks and foot bridges) in Florida were examined to evaluate potential impacts from chromated copper arsenate (CCA), a common wood preservative. Eight of the nine structures were confirmed to have been treated with CCA. Soils collected were evaluated for arsenic, chromium, and copper concentrations as well as pH, volatile solids content and particle size distribution. Two types of soil samples were collected: a soil core and surface soil samples (upper 2.5 cm). One soil core was collected from below each deck and one control core was collected from an area removed from one of the structures. Eight or nine surface soil samples were collected in a grid-like fashion from beneath each structure. Equal numbers of surface control samples were collected from areas away from the structures. Metal concentrations were elevated in both the soil cores and surface samples collected from below the CCA-treated structures. Core samples showed elevated concentrations of metals at depths up to 20 cm. The arithmetic mean concentrations of arsenic, chromium, and copper in the 65 surface soil samples collected from below CCA-treated structures were 28.5 mg/kg, 31.1 mg/kg, and 37.2 mg/kg, respectively, whereas the mean concentrations of arsenic, chromium, and copper in the control samples were 1.34 mg/kg, 8.62 mg/kg, and 6.05 mg/kg, respectively. Arsenic concentrations exceeded Florida's risk-based soil cleanup target level (SCTL) for residential settings in all 65 surface soil samples. The industrial setting SCTL was exceeded in 62 of the 65 samples.     

Arsenic in groundwater and its health risk assessment in drinking water of Mailsi,Punjab, Pakistan

The present study was aimed at assessing drinking water quality regarding arsenic (As) and its impact on health from Mailsi (Punjab), Pakistan. Forty-four groundwater samples were collected from two sites, Sargana and Mailsi. Arsenic and other cations were determined by atomic absorption spectrophotometer, whereas the anions were determined either through titration or spectrophotometer. The results revealed that dominant anions were HCO₃^? and Cl^?, Ca⁺² was the dominant cation, and overall water chemistry of the area was CaMgHCO₃^? type. Arsenic concentrations were high, ranging from 11 to 828 µg/L that crossed the World Health Organization permissible limits. Likewise, higher SO₄^?2 concentrations ranging from 247 to 1053 mg/L were observed. The health risk index was higher in the Sargana site, which employed the differences in terms of higher Average Daily Dose, Hazard Quotient, and Carcinogenic Risk of arsenic, which is unsuitable for drinking purposes. The area seems to be at high risk due to arsenic pollution and wells have never been tested for arsenic concentrations earlier; therefore, necessary measures should be taken to test the wells with respect to arsenic.     

Arsenic uptake and accumulation in rice (Oryza sativa L.) irrigated with contaminated water

Long-term use of arsenic contaminated groundwater to irrigate crops, especially paddy rice (Oryza sativaL.) has resulted in elevated soil arsenic levels in Bangladesh. There is, therefore, concern regarding accumulation of arsenic in rice grown on these soils. A greenhouse pot experiment was conducted to evaluate the impact of arsenic-contaminated irrigation water on the growth and uptake of arsenic into rice grain, husk, straw and root. There were altogether 10 treatments which were a combination of five arsenate irrigation water concentrations (0–8 mg As l^–1) and two soil phosphate amendments. Use of arsenate containing irrigation water reduced plant height, decreased rice yield and affected development of root growth. Arsenic concentrations in all plant parts increased with increasing arsenate concentration in irrigation water. However, arsenic concentration in rice grain did not exceed the maximum permissible limit of 1.0 mg As kg^–1. Arsenic accumulation in rice straw at very high levels indicates that feeding cattle with such contaminated straw could be a direct threat for their health and also, indirectly, to human health via presumably contaminated bovine meat and milk. Phosphate application neither showed any significant difference in plant growth and development, nor in As concentrations in plant parts.     

Studies on Fractionation of Arsenic in Soil in Relation to Crop Uptake

Widespread arsenic (As) contamination in West Bengal and Bangladesh is of great concern as it affects millions of people due to its toxicity. Groundwater, when used for irrigation, helps entry of arsenic into the food chain via a soil-plant-animal continuum. In this study the extent of geo accumulation is measured in order to assess the degree of As contamination in soil. A sequential fractionation study of As revealed the concentration of different arsenic fractions in the order: As held at the internal surfaces of soil aggregates (20.7%) > freely exchangeable As (20.3%) > calcium associated As (18.7%) > chemisorbed As (17%) > residual As (15.7%) > labile As (3.29%). The variation in fractions may be attributed to the mineralogical make-up of soils along with some physicochemical factors. Statistical correlations and path analyses revealed that total and Olsen extractable arsenic (plant available arsenic) are dependent upon the As held at the internal surfaces of soil aggregates and chemisorbed arsenic fraction, which are directly influenced by the mineralogy of these experimental soils. The crop uptake by Kharif rice and mustard grown in these areas also corroborates the above fact. The poor reflection of exchangeable forms of soil arsenic in crop availability revealed that arsenic has undergone transformation via minerals through the continuous use of arsenic-laden water for irrigation.     

Ecotoxicity Test Data for Total Petroleum Hydrocarbons in Soil: Plants and Soil-Dwelling Invertebrates

Ecotoxicity benchmarks for petroleum mixtures can be used in a screening-level ecological risk assessment. Data from studies evaluating the toxicity of total petroleum hydrocarbons (TPH) to plants and soil invertebrates were reviewed for possible application to soil benchmark development. Toxicity data included LOAECs; estimated EC25s, EC20s, and LC50s; effective concentrations that caused greater than a 20% level of effect; and NOAECs. The variabilities in petroleum material, chemical analytical methodology, age of hydrocarbon-soil contact, nutrient amendment, and measured effects levels did not permit much meaningful aggregation of the data. Tenth, twenty-fifth, and fiftieth percentiles of toxicity and no-effects data are presented for unaggregated results within studies. Effects on invertebrates often occurred at concentrations of TPH lower than those associated with effects on plants. Lighter mixtures generally were associated with lower ranges of effects concentrations than heavier crude oil. Few aged and non-aged samples were available from the same study, and these did not show obvious trends regarding toxicity. Similarly, the addition of nutrients to promote bioremediation was not observed across studies to alter effective or nontoxic concentrations in a systematic way. Existing toxicity data are not sufficient to establish broadly applicable TPH ecotoxicity screening benchmarks with much confidence, even for specific mixtures.     

Estimation of Multimedia Inorganic Arsenic Intake in the U.S. Population

Arsenic is widely distributed in the environment by natural and human means. The potential for adverse health effects from inorganic arsenic depends on the level and route of exposure. To estimate potential health risks of inorganic arsenic, the apportionment of exposure among sources of inorganic arsenic is critical. In this study, daily inorganic arsenic intake of U.S. adults from food, water, and soil ingestion and from airborne particle inhalation was estimated. To account for variations in exposure across the U.S., a Monte Carlo approach was taken using simulations for 100,000 individuals representing the age, gender, and county of residence of the U.S. population based on census data. Our analysis found that food is the greatest source of inorganic arsenic intake and that drinking water is the next highest contributor. Inhalation of airborne arsenic-containing particles and ingestion of arsenic-containing soils were negligible contributors. The exposure is best represented by the ranges of inorganic arsenic intake (at the 10^th and 90^th percentiles), which were 1.8 to 11.4 µg/day for males and 1.3 to 9.4 µg/day for females. Regional differences in inorganic arsenic exposure were due mostly to consumption of drinking water containing differing inorganic arsenic content rather than to food preferences.     

Arsenic in Seafood: Speciation Issues for Human Health Risk Assessment

Major sources of arsenic exposure for humans are foods, particularly aquatic organisms, which are called seafood in this report. Although seafood contains a variety of arsenicals, including inorganic arsenic, which is toxic and carcinogenic, and arsenobetaine, which is considered nontoxic, the arsenic content of seafood commonly is reported only as total arsenic. A goal of this literature survey is to determine if generalizable values can be derived for the percentage of total arsenic in seafood that is inorganic arsenic. Generalizable values for percent inorganic arsenic are needed for use as default values in U.S. human health risk assessments of seafood from arsenic-contaminated sites. Data from the worldwide literature indicate the percent of inorganic arsenic in marine/estuarine finfish does not exceed 7.3% and in shellfish can reach 25% in organisms from presumably uncontaminated areas, with few data available for freshwater organisms. However, percentages can be much higher in organisms from contaminated areas and in seaweed. U.S. site-specific data for marine/estuarine finfish and shellfish are similar to the worldwide data, and for freshwater finfish indicate that the average percent inorganic arsenic is generally < 10%, but ranges up to nearly 30%. Derivation of nationwide defaults for percent inorganic arsenic in fish, shellfish, and seaweed collected from arsenic-contaminated areas in the United States is not supported by the surveyed literature.     

Identification and Characterization of Arsenic and Metal Compounds in Contaminated Soil,Mine Tailings,and House Dust Using Synchrotron-Based Microanalysis

A comprehensive understanding of the risk associated with metal-rich soils and other materials includes identification of the solid phases hosting the metals. Synchrotron microanalysis provides a powerful diagnostic tool to characterize metal-bearing particles in mine tailings, soils, lake sediments, windblown dust, and household dust. A near simultaneous combination of X-ray fluorescence, diffraction, and absorption experiments using a microfocused beam can provide information on elemental concentrations, crystal structure, and oxidation state of individual particles. This approach can distinguish multiple metal-hosting minerals and industrial compounds in a single sample. Our objective is to provide examples of the application of this technique to a range of materials representing potential risk to human or ecosystem health. These examples include arsenic-contaminated materials and metal-rich household dust. We have identified grains of scorodite and other arsenate minerals in mine tailings and associated airborne dust, arsenic trioxide in organic soils near an ore roaster, metallurgical products dispersed to the environment, and various metal-rich particles in household dust. A comparison of chemical analysis of individual particles using electron microprobe analysis and synchrotron-based X-ray fluorescence analysis is provided.     

A Model to Derive Soil Criteria for Benzene Migrating from Soil to Dwelling Interior in Homes with Crawl Spaces

The establishment of Australian soil criteria for volatile hydrocarbons such as benzene has been limited due to the lack of a suitable transport model to predict human exposures. In a confined environment representing worst case exposure, the inhalation of volatile hydrocarbons from sub-surface regions may be used to establish health-based soil criteria. A volatilisation model is presented for the case of a crawl space home which is a common housing design in Australia. The model is used to estimate a cumulative indoor human dose (CIHD) based on one-dimensional movement from a finite subsurface source through soil to the dwelling interior. A non-homogeneous surface boundary condition is represented where the volatile is not immediately swept away from the air/soil boundary. Time-dependent differential equations established to represent transport are solved using Laplace transforms. Australian experimental field data are used in considering mixing, dilution, ventilation and sink effects and first-order soil and air degradation of the volatile incorporated. A CIHD from the model is compared to various benzene exposure standards to determine a criterion for benzene in soil. Sensitivity analysis has revealed that the dominant influencing parameters are those relating to dwelling characteristics and not soil properties or the physico-chemical properties of the volatile. Each of the group-input parameters has been found to act virtually independently in the model presenting the potential for model refinement and establishment of a generic soil criterion for benzene.     

Arsenic in Michigan Soil: Spatial Stratification for Environmental Regulatory Purposes

State environmental regulatory agencies in the U.S. often establish a default background standard for naturally occurring elements in the soil, water, and air. The background standard is determined and then used as a benchmark across the entire jurisdiction. A variety of statistical techniques are used to determine this standard, but often ignore any inherent spatial dependencies within the jurisdiction. If the analysis indicates a specific site exceeds the default standard, additional background sampling and analysis must usually be performed. Frequently, this additional sampling is found to be unnecessary simply because the natural background levels were elevated for this particular site. Conversely, potential contamination may be overlooked in areas where the natural background levels are much lower. Thus, a single default background standard seems inadequate within this context.

This paper proposes the use of dissimilarity coefficients based on kriging estimates as a means to regionalize background standards. Along with cluster analysis techniques, these dissimilarity coefficients provide a means to stratify the population into geographic sub-areas. A regulatory agency may now define multiple default background standards based on geographic location. To illustrate, this paper examines a case study concerning residential soil arsenic for 83 Michigan counties.     

Arsenic exposure levels of petrochemical workers in three workplace settings in Rayong Province,Thailand

Background: Crude oil and natural gas are often contaminated with arsenic. As a carcinogen, arsenic contamination in the workplace is of concern, particularly when urinary arsenic levels are higher than the standard. The aim of this study was to identify exposure sources of arsenic among petrochemical workers. Methods: A total of 188 operators and 30 office workers participated in the study. Ninety-three workplace air samples, three main meals in five consecutive days, and drinking water were collected from each participant. Urine was collected at the end of the day after the last food sample was collected from each subject. Urine samples where arsenic concentration exceeded 100 mg/L were further analyzed to identify species. Results: The average arsenic concentrations in operators' and office workers' food and urine were 0.55 ± 1.00 and 0.49 ± 0.67 mg/kg; and 76.43 ± 107.36 and 149.92 ± 200.28 mg/L, respectively. The arsenic concentrations in air and water were well below their standards. The urinary arsenic correlated well with arsenic in the food but not in the air and water. Conclusion: Occupational exposure to arsenic among operators and office workers was lower than 1% TLV (Threshold limit value) and did not differ significantly. The major source of arsenic exposure Q2 was food.     

Using Betula pendula and Telephora caryophyllea for Soil Pollution Assessment

The concentrations of available arsenic, copper, lead, and zinc in the soil, and the concentration of these elements in vegetal tissues were measured. The most common species at the sites were studied. All the species that were analyzed took up pollutants and could indicate polluted soil. However, all the studied species did not fit to map pollution. The birch (Betula pendula) and most of the fungi species had still quite low concentrations in their tissues compared with the available concentrations in the soil. No direct correlation between the pollution content in the soil and in the vegetation tissues could be observed. Specimens of Thlaspi caerulescens were accumulating zinc. Of the four fungi species collected, only Thelephora caryophyllea seemed to accumulate actively in the studied pollutants. Moreover, it was possible to use an arsenic test with the fungi, which is also interesting from the perspective of preliminary assessment of the degree of pollution. A qualitative judgement of the soil pollution is possible by examining the plant material. To obtain a more quantitative and complete mapping, the method has to be developed further and completed with other investigations when vegetation is missing.     

Sensitivity Analysis of U.S. EPA's Estimates of Skin Cancer Risk from Inorganic Arsenic in Drinking Water

The current U.S. Environmental Protection Agency's (USEPA's) risk analysis on the Integrated Risk Information System (IRIS) for arsenic in drinking water is based on an epidemiological study of skin cancer in Taiwan. Assumptions used in the USEPA application of the multistage-Weibull model for risk estimation were varied to assess the effect on predicted risk of skin cancer to the U.S. population at arsenic concentrations of 1 to 50?µg/L in drinking water. Among the assumptions tested, the only notable change in risk estimates was a reduction when the arsenic concentration used as representative for Taiwan villages in the low range (<300?µg/L) was increased to the 75th percentile (245?µg/L) in place of the mean used in the USEPA analysis (170?µg/L), but the representative value for Taiwan villages in the high range (≥600?µg/L) was not increased simultaneously to the 75th percentile. Additionally, a simulation study was conducted using records of arsenic measurements in wells from the same period and region of Taiwan as the original study. The exposure-response curve estimated from 60 villages (60 data points) differed only marginally from the outcome when data were summarized into four data points (as in the USEPA skin cancer analysis). Briefly discussed are differences between the study area of Taiwan and the U.S. in nutritional status and consumption of inorganic arsenic in food that might bias predicted U.S. skin cancer risks.     

Finding A Niche for Soil Microbial Toxicity Tests in Ecological Risk Assessment

Soil microbial toxicity tests are seldom used in ecological risk assessments or in the development of regulatory criteria in the U.S. The primary reason is the lack of an explicit connection between these tests and assessment end-points. Soil microorganisms have three potential roles with respect to ecological assessment endpoints: properties of microbial communities may be end-points; microbial responses may be used to estimate effects on plant production; and microbial responses may be used as surrogates for responses of higher organisms. Rates of microbial processes are important to ecosystem function, and thus should be valued by regulatory agencies. However, the definition of the microbial assessment endpoint is often an impediment to its use in risk assessment. Decreases in rates are not always undesirable. Processes in a nutrient cycle are particularly difficult to define as endpoints, because what constitutes an adverse effect on a process is dependent on the rates of others. Microbial tests may be used as evidence in an assessment of plant production, but the dependence of plants on microbial processes is rarely considered. As assessment endpoints are better defined in the future, microbial ecologists and toxicologists should be provided with more direction for developing appropriate microbial tests.     

Distribution of Arsenic,Antimony, and Thallium in Soil in Kavadarci and its Surroundings,Republic of Macedonia

The aim of this study is to present a spatial distribution of As, Sb, and Tl in topsoil and subsoil in the Kavadarci region, Republic of Macedonia. In total, 344 soil samples were collected from 172 locations (0–5 cm and 20–30 cm) in an area of 360 km². ICP-MS was applied for the determination of the invesgated elements. It was found that the highest contents of As, Sb, and Tl were on Holocene alluvium of the river Crna Reka, where average concentrations exceeded the average of the total investigated area by two times for As, three for Tl, and more than five times for Sb. The enrichment of the Holocene alluvium of the river Crna Reka is supposed to be a consequence of natural erosion from Allchar mine deposits on Ko?uf Mountain and also from mining activities in the past.     

Risk-Based Zoning Strategy for Soil Remediation at an Industrial Site

After determining at an early stage of the project that the future land use of this New Jersey chemical manufacturing site remain industrial in nature, the site was zoned according to risk. The chemicals of concern (COCs) at the site included relatively low levels of mono- and polynuclear aromatic hydrocarbons, chlorinated aliphatics, as well as other volatile and semivolatile compounds. Direct human exposure scenarios were the key to the mitigation of risks related to soils because the groundwater migration pathway was already interrupted using groundwater recovery. A focused remedial strategy was developed to ensure that the exposure pathways (inhalation, ingestion, and dermal contact) are alleviated and the remedial measures are protective to the workers operating and/or maintaining the site. The risk evaluation process included a preliminary risk assessment (Tier 1) based on a comparison with pertinent soil cleanup criteria, a prioritization analysis to rank zones, chemicals and pathways of concern, and an application of the Risk Based Corrective Action (RBCA) approach (Tier 2) for construction worker exposure scenario. The risk assessment identified selected areas that would benefit from remedial actions. Prioritization Analysis classified the site into five high-priority (comprising 97% of the total health-based risk), three medium-priority (contributing to remaining 2 to 3% of the risk), and adequately protected areas. The boundaries and volumes of affected areas were delineated based on confirmatory soil sampling and statistical analyses. The remedial technologies selected for the site have achieved appropriate reduction in risk to comply with all State regulations and include (in addition to the institutional controls): ??Capping the site where only immobilesemivolatile contaminants are present ??Excavation and on-site treatment of the soils impacted by volatile organic com pounds through ex situ low temperature desorption, or alternative “biopile” treatment and natural attenuation, and ??Excavation and off-site disposal of limited volumes of soils This risk-based, integral approach helped identify the real significance of contamination present at the site and facilitated the development of suitable and adequate remedies. Had not it been for this approach, the mere comparison with soil cleanup criteria would have unnecessarily resulted in denoting all areas as nuisance contributors, and thus requiring some actions. New Jersey Department of Environmental Protection (NJDEP) has approved this approach and contributed to its accomplishment.     

土壤种子库与矿业废弃地植被恢复研究I.Leonard瓶-罐装置在土壤种子库检测中的应用

１前言土壤种子库的组成和动态的检测主要有两种方法,其一是把土壤样品铺在垫有沙子（经消毒除去沙子内可能有的种子）的花盆或其它发芽框上,给予合适条件使土样中的种子萌发,记录幼苗数及种类［１～５］;另一种是用物理方法分离土样直接得到种子,检测种子活力和统计...