Comparison,Validation, and Use of Models for Predicting Indoor Air Quality from Soil and Groundwater Contamination

The use of models to predict indoor air quality and health risk for the soil vapor transport to indoor air pathway is commonplace; however, there is significant uncertainty surrounding processes and factors affecting this pathway, and the accuracy of models used. Available screening models were evaluated through a review of model characteristics and sensitivity, and through comparisons to measured conditions at field sites. Model simulations and comparisons to field data indicate that the vapor attenuation ratio (α) is highly sensitive to certain processes (e.g., biodegradation and ad-vection) and input parameters. Comparisons of model predicted to measured a values indicate that models based on the Johnson and Ettinger (1991) framework in most cases result in predictions that are conservative by up to one to two orders of magnitude for field sites that were assessed, providing that appropriate input parameters are used. However, for sites where the advection potential is high, these models may not be conservative. The potential for advective transport of vapors into building may be significant for sites with shallow contamination, high permeability soil and foundation and high building underpressurization. The paper concludes with possible tiered management framework for the soil vapor pathway.     

Seasonal Variations of Indoor Microbial Exposures and Their Relation to Temperature,Relative Humidity,and Air Exchange Rate

Indoor microbial exposure has been related to adverse pulmonary health effects. Exposure assessment is not standardized, and various factors may affect the measured exposure. The aim of this study was to investigate the seasonal variation of selected microbial exposures and their associations with temperature, relative humidity, and air exchange rates in Danish homes. Airborne inhalable dust was sampled in five Danish homes throughout the four seasons of 1 year (indoors, n = 127; outdoors, n = 37). Measurements included culturable fungi and bacteria, endotoxin, N-acetyl-beta-d-glucosaminidase, total inflammatory potential, particles (0.75 to 15 μm), temperature, relative humidity, and air exchange rates. Significant seasonal variation was found for all indoor microbial exposures, excluding endotoxin. Indoor fungi peaked in summer (median, 235 CFU/m³) and were lowest in winter (median, 26 CFU/m³). Indoor bacteria peaked in spring (median, 2,165 CFU/m³) and were lowest in summer (median, 240 CFU/m³). Concentrations of fungi were predominately higher outdoors than indoors, whereas bacteria, endotoxin, and inhalable dust concentrations were highest indoors. Bacteria and endotoxin correlated with the mass of inhalable dust and number of particles. Temperature and air exchange rates were positively associated with fungi and N-acetyl-beta-d-glucosaminidase and negatively with bacteria and the total inflammatory potential. Although temperature, relative humidity, and air exchange rates were significantly associated with several indoor microbial exposures, they could not fully explain the observed seasonal variations when tested in a mixed statistical model. In conclusion, the season significantly affects indoor microbial exposures, which are influenced by temperature, relative humidity, and air exchange rates.     

Contribution of lead in soil to children’s lead burden,an update

Abstract

Blood lead levels in children in the USA have dropped dramatically since lead in food, air and drinking water was reduced. In inner cities and older residential areas, increased lead exposure may still be a problem because of dilapidated housing with high lead paint levels. In these areas, at mining sites and around smelters lead levels in soil may be very high. A review of many studies indicates that lead in soil or mine tailings does not make a meaningful contribution to lead absorption by children. The contribution of lead in soil to overall exposure, if any, lies within the variation of the analytical method for blood lead measurements. The results of exposure studies in the pediatric population reviewed in this article do not support exposure predictions for children under 6 years of age based on the US EPA Integrated Exposure Uptake Biokinetic Model (using default parameters or using results obtained with in vitro digestion models). They also do not support predictions based on the percent of solubility of lead in soil (accessibility studies).     

Assessing the Bioavailability and Risk from Metal-Contaminated Soils and Dusts

Exposure to contaminated soil and dust is an important pathway in human health risk assessment. Physical and chemical characteristics and biological factors determine the bioaccessibility/bioavailability of soil and dust contaminants. Within a single sample, contamination may arise from multiple sources of toxic elements that may exist as different species that impact bioavailability. In turn, the bioaccessibility/bioavailability of soil and dust contaminants directly impacts human health risk. Research efforts focusing on development and application of in vitro and in vivo methods to measure the bioaccessibility/bioavailability of metal-contaminated soils have advanced in recent years. The objective of this workshop was to focus on developments in assessing the bioaccessibility/bioavailability of arsenic-contaminated soils, metals’ contamination in urban Canadian residences and potential children's exposures to toxic elements in house dust, an urban community-based study (i.e., West Oakland Residential Lead Assessment), bioavailability studies of soil cadmium, chromium, nickel, and mercury and human exposures to contaminated Brownfield soils. These presentations covered issues related to human health and bioavailability along with the most recent studies on community participation in assessing metals’ contamination, studies of exposures to residential contamination, and in vitro and in vivo methods development for assessing the bioaccessibility/bioavailability of metals in soils and dusts.     

川西亚高山针叶林树种云杉和冷杉土壤酸碱性差异及其机制

比较了川西亚高山针叶林主要树种粗枝云杉(Picea asperata)和岷江冷杉(Abies faxoniana)样地各土层(0—5 cm、5—10cm、10—20 cm)土壤pH值差异,并从两树种养分吸收和养分归还相关累积H~+输入方面探究其差异原因。研究结果表明:云杉样地各土层土壤pH值均显著高于冷杉样地(P0.05);云杉样地地被物累积H~+输入显著低于冷杉样地(P0.05);云杉样地凋落物中P、Mg、N、C平均浓度显著低于冷杉(P0.05),而Ca、C/N、木质素/N、C/P显著高于冷杉样地(P0.05),两树种凋落物中木质素、K平均浓度无显著差异。云杉和冷杉凋落物化学特性主成分分析PC_1、PC_2方差贡献率分别为73.7%和15.6%,累积方差贡献率为89.4%,其中PC_1主要综合Ca、C/P、C/N、木质素/N、P、N、Mg的信息;PC_2主要综合木质素、K、C的信息。各土层土壤pH值均与地被物累积H~+输入显著负相关,与PC_1样本分数显著正相关。研究结论:云杉和冷杉样地土壤pH值存在显著树种差异,且云杉使土壤pH值变大,冷杉使土壤pH值变小,这主要与地被物形成以及凋落物化学特性有关,即与凋落物的量和凋落物分解速率、凋落物养分归还率密切相关。     

Mycotoxins in indoor environments

Exposure to mycotoxins produced by toxigenic molds growing in damp indoor spaces has been difficult to assess. Monitoring methods limit the characterization of inhalation exposure of any bioaerosol, especially that of mycotoxins. Biomarkers promise better ability to determine mycotoxin exposures 1.) through direct measures of toxins and their products in human tissues, 2.) through immunochemical methods, and 3.) measures of effect through novel approaches,e.g., proteomics or genomics. This paper summarizes both the problems inherent in measuring exposures and some of the promising methods that could help to resolve the current impasse. Presented at the 27^th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005.     

Seasonal Changes in Soil Respiration with An Elevation Gradient in <i>Abies nephrolepis</i> (Trautv.) Maxim. Forests in North China

Soil respiration (Rs) plays an important role in regulating carbon cycle of terrestrial ecosystems and presents temporal and spatial heterogeneity. Abies nephrolepis is a tree species that prefers the cold and wet environment and is mainly distributed in Northeast Asia and East Asia. The Rs variations of Abies nephrolepis forests communities are generally environmental-sensitive and can effectively reflect the adaptive responses of forest ecosystems to climate change. In this study, the growing-seasonal variations of Rs, soil temperature, soil water content and soil properties of Abies nephrolepis forests were analyzed along an altitude gradient (2000, 2100, 2200 and 2300 m) over two years on Wutai Mountain in North China. As the main results showed, soil respiration keeps the same change trend as soil temperature and reached peaks in July at 2000 m in 2019 and 2020. During 26^th July to 25^th October in 2019 and 27^th May to 23^rd October in 2020, on the whole, the soil temperature independently explained 76.2% of Rs variations while the soil water content independently explained 26.8%. Soil temperature and soil water content jointly explained 81.8% of Rs variations. Soil properties explained 61.8% and 69.6% of Rs variation in 2019 and 2020, respectively. Soil organic carbon content and soil enzyme activity had the signifi- cant (P < 0.01) negative and positive relationships, respectively, with Rs variation. With altitudes evaluated from 2000 to 2300 m, soil respiration temperature sensitivity (Q₁0) and the soil organic carbon content increased by 12.4% and 10.4%, respectively, while invertase activity, cellulase activity and urease activity dropped by 41.2%, 29.45% and 38.19%, respectively. The results demonstrate that (1) soil temperature is the major factor affecting Rs variations in Abies nephrolepis forests; (2) weakened microbial carbon metabolism in high-altitude areas results in the accumulation of soil organic carbon; (3) with a higher Q₁, forest ecosystems in high-altitude areas might be more easily affected by climate change; (4) climate warming might accelerate the consumption of soil organic carbon sink in forest ecosystems, especially in high-altitude areas.     

Impacts of an anomalously warm year on soil CO2 efflux in experimentally manipulated tallgrass prairie ecosystems

Modeling analyses suggest that an increase in growth rate of atmospheric CO₂ concentrations during an anomalously warm year may be caused by a decrease in net ecosystem production (NEP) in response to increased heterotrophic respiration (R_h). To test this hypothesis, 12 intact soil monoliths were excavated from a tallgrass prairie site near Purcell, Oklahoma, USA and divided among four large dynamic flux chambers (Ecologically Controlled Enclosed Lysimeter Laboratories (EcoCELLs)). During the first year, all four EcoCELLs were subjected to Oklahoma air temperatures. During the second year, air temperature in two EcoCELLs was increased by 4°C throughout the year to simulate anomalously warm conditions. This paper reports on the effect of warming on soil CO₂ efflux, representing the sum of autotrophic respiration (R_a) and R_h. During the pretreatment year, weekly average soil CO₂ efflux was similar in all EcoCELLs. During the late spring, summer and early fall of the treatment year, however, soil CO₂ efflux was significantly lower in the warmed EcoCELLs. In general, soil CO₂ efflux was correlated with soil temperature and to a lesser extent with moisture. A combined temperature and moisture regression explained 64% of the observed variation in soil CO₂ efflux. Soil CO₂ efflux correlated well with a net primary production (NPP) weighted greenness index derived from digital photographs. Although separate relationships for control and warmed EcoCELLs showed better correlations, one single relationship explained close to 70% of the variation in soil CO₂ efflux across treatments and years. A strong correlation between soil CO₂ efflux and canopy development and the lack of initial response to warming indicate that soil CO₂ efflux is dominated by R_a. This study showed that a decrease in soil CO₂ efflux in response to a warm year was most likely dominated by a decrease in R_a instead of an increase in R_h.     

Prevalence of dermal pathway dominance in risk assessment of contaminated soils: A survey of superfund risk assessments, 1989–1992

Exposure to soil‐borne contaminants can occur through ingestion, inhalation and/or dermal absorption. A study was undertaken to assess the relative frequency with which dermal exposures are predicted to pose the greatest risk attributable to contaminated soils in Superfund risk assessments. Screening of over 200 risk assessments from the period 1989–1992 resulted in identification of 37 sites at which projected lifetime excess cancer risks attributed to dermal contact with soil were greater than the nominal regulatory threshold of 1.10^‐4. At 19 of these sites, the dermal/soil pathway is estimated to contribute the largest carcinogenic risk associated with surface soil contamination, and may therefore drive cleanup of that medium. At 9 of the sites, the dermal/soil pathway is predicted to present a higher carcinogenic risk than any other pathway. Chemical contaminant type and estimates of soil adherence and surface area exposed appear to be the primary factors that distinguish sites at which dermal/soil pathway carcinogenic risk estimates are elevated relative to other exposure pathways. Quantification of exposure parameters, especially those related to behavior, remains a significant need.     

Comparison of the urban heat island intensity quantified by using air temperature and Landsat land surface temperature in Hangzhou,China

This study compared different measures of urban heat island (UHI) intensity, which were calculated using both air temperature (T_air) at a height of 1.5 m and Landsat land surface temperature (LST) in Hangzhou, China. Two UHI-driven indicators (range and magnitude) and two land-cover-driven indicators (urban-rural and urban-agriculture) were calculated to quantify the UHI intensity based on hourly T_air from five stations and fifteen Landsat 5 LST images. Pearson correlation testing and a moving average times series of the previous 30 days were used to investigate the relationship between UHI intensities calculated by different indicators and data. The results indicate that the land-cover-driven indicators explain UHI better than the UHI-driven indicators, while the calculated values of UHI intensity using Landsat LST and hourly T_air are not comparable. We also investigated the influence of weather conditions on UHI intensity. Generally, Landsat-LST-based UHI performs best on hot sunny days, while T_air-based UHI has a better chance during the nighttime following a dry sunny day. This study suggests that the value of UHI intensity can be influenced by the selected indicators, the data used, the acquisition time and the weather conditions. Thus, these factors should be considered when comparing UHI intensity between different cities or quantifying their influences (e.g., population size, land use and land cover change) on UHI intensity.     

A survey of airborne algae and cyanobacteria within the indoor environment of an office building in Kuala Lumpur,Malaysia

This study investigates the occurrence of airborne algae and cyanobacteria (AAC) within the indoor environment of an office building in Kuala Lumpur, Malaysia. Samples of air, wall scrapings and soils of potted plants were collected from various sites within the building and surrounding areas. In addition, AAC were collected by exposing a culture medium to the indoor air. Based on the cultured material, 14 taxa of AAC consisting of cyanobacteria such as Phormidium angustissima and Chroococcus minor and chlorophytes such as Chlorella vulgaris and Chlorococcum humicola were recorded. The surrounding areas of the building recorded the highest occurrence (75%) of AAC. Within the building, the highest occurrence of AAC (45%) was recorded on the lower ground floor, an area exposed to the outdoor environment. Some of the AAC recorded were also detected in the wall scraping and soil samples. Areas with heavy human movement appeared to have high occurrence of AAC. Human movement appeared to be an important factor in affecting the dispersal of the AAC.     

Preliminary surveys of outdoor and indoor aeromycobiota in Uganda

This investigation was conducted during the period of March through June 1998 to trap, enumerate and identify the different airborne fungi in a variety of microhabitats of outdoor and indoor environments in different localities of Uganda. The settle plate method was used and Czapek-Dox agar was the isolation medium. A total of 47 genera and 61 species in addition to some other unidentified airborne fungi were trapped from all exposures at outdoor (39 genera and 52 species) and indoor (35 and 49) environments. The total fungal catches of outdoor airspora obtained from all exposures (and even in most individual exposures) were more than twice (5222 colonies) of that of the indoor ones (4361) when the exposure periods are taken into consideration. It is worth mentioning that the most highly polluted sites were either parks, forests or river banks for outdoor exposures, or teaching laboratory, library, laterines or bathrooms for indoor exposures. The most prevalent fungi from both outdoor and indoor microhabitats being species of Mycosphaerella, Yeasts, Penicillium, Fusarium, Aspergillus,Cochliobolus and Alternaria. However, several others were trapped frequently from either outdoor or indoor environments. On the other hand, several others were trapped only, but not frequently (in low or rare instances) from either outdoor or indoor microhabitats. The implications of these airborne spores are also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Reductions in daily soil temperature variability increase soil microbial biomass C and decrease soil N availability in the Chihuahuan Desert: potential implications for ecosystem C and N fluxes

Maximum and minimum soil temperatures affect belowground processes. In the past 50 years in arid regions, measured reductions in the daily temperature range of air (DTR_air) most likely generated similar reductions in the unmeasured daily temperature range of soil (DTR_soil). However, the role of DTR_soil in regulating microbial and plant processes has not been well described. We experimentally reduced DTR_soil in the Chihuahuan Desert at Big Bend National Park over 3 years. We used shade cloth that effectively decreased DTR_soil by decreasing daily maximum temperature and increasing nighttime minimum temperature. A reduction in DTR_soil generated on average a twofold increase in soil microbial biomass carbon, a 42% increase in soil CO₂ efflux and a 16% reduction in soil NO₃^?–N availability; soil available NH₄⁺–N was reduced by 18% in the third year only. Reductions in DTR_soil increased soil moisture up to 15% a few days after a substantial rainfall. Increased soil moisture contributed to higher soil CO₂ efflux, but not microbial biomass carbon, which was significantly correlated with DTR_soil. Net photosynthetic rates at saturating light (A_sat) in Larrea tridentata were not affected by reductions in DTR_soil over the 3 year period. Arid ecosystems may become greater sources of C to the atmosphere with reduced DTR_soil, resulting in a positive feedback to rising global temperatures, if increased C loss is not eventually balanced by increased C uptake. Ultimately, ecosystem models of N and C fluxes will need to account for these temperature‐driven processes.     

A report on Penicillium in the intramural and extramural air of residential areas of Nagpur city (India)

Prevalence of different species of Penicillium and their concentrations per cubic meter of air were evaluated with the use of Hi-Air sampler system Mark II (Hi-Media Laboratories Ltd., India) in the air of homes (bed-rooms) at four different sites in Nagpur. At each of these sites, air sampling was done fortnightly in triplicate for 2 years duration from June 2000 to May 2002. The sampling was also done in triplicate for the outdoor air in the vicinity of each home on the same day immediately after the indoor sampling was over. The mean concentration of Penicillium colony forming units at four different sites in the indoor air was 32, 46.9, 35 and 35.4 CFU/m³, respectively, whereas in the outdoor air at these same four sites, the mean concentration was 24, 28, 25 and 25.8 CFU/m³ respectively. The Penicillium concentration in the indoor air was found to be higher in winter than in other seasons (ANOVA, p < 0.05). Concentration of Penicillium spp. in intramural environment was always higher than that in extramural environment. Statistically significant difference existed between intramural and extramural environments at all the sites, with maximum difference at a site, which is old crowded area of the city. During the 2-years investigations, 11 species of Penicillium were isolated from the indoor air while nine species were isolated from the air outside the homes. The dominant species of Penicillium in indoor as well as outdoor air were P. citrinum (33.78 and 32.81), P. oxalicum (19.70 and 22.60), and P. chrysogenum (17.64 and 14.50). The percentage of the Penicillium in the indoor air was 10.70 while it was 8.36 in outdoor air. Indoor air showed the presence of P. glaber and P. sclerotiorum, which were absent in the outdoor air.     

Coordination of photosynthetic traits across soil and climate gradients

“Least-cost theory” posits that C₃ plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia-wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO₂ drawdown (lower ratio of leaf internal to ambient CO₂, C_i:C_a) during light-saturated photosynthesis, and at higher leaf N per area (N_area) and higher carboxylation capacity (V_{cmax 25}) for a given rate of stomatal conductance to water vapour, g_sw. These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the N_area–g_sw and V_{cmax 25}–g_sw slopes, and negative effects on C_i:C_a. The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in individual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low-relief landscapes with highly leached soils. Least-cost theory provides a valuable framework for understanding trade-offs between resource costs and use in plants, including limiting soil nutrients.     

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.     

A report on <Emphasis Type="Italic">Penicillium</Emphasis> in the intramural and extramural air of residential areas of Nagpur city (India)

Prevalence of different species of Penicillium and their concentrations per cubic meter of air were evaluated with the use of Hi-Air sampler system Mark II (Hi-Media Laboratories Ltd., India) in the air of homes (bed-rooms) at four different sites in Nagpur. At each of these sites, air sampling was done fortnightly in triplicate for 2 years duration from June 2000 to May 2002. The sampling was also done in triplicate for the outdoor air in the vicinity of each home on the same day immediately after the indoor sampling was over. The mean concentration of Penicillium colony forming units at four different sites in the indoor air was 32, 46.9, 35 and 35.4 CFU/m³, respectively, whereas in the outdoor air at these same four sites, the mean concentration was 24, 28, 25 and 25.8 CFU/m³ respectively. The Penicillium concentration in the indoor air was found to be higher in winter than in other seasons (ANOVA, p < 0.05). Concentration of Penicillium spp. in intramural environment was always higher than that in extramural environment. Statistically significant difference existed between intramural and extramural environments at all the sites, with maximum difference at a site, which is old crowded area of the city. During the 2-years investigations, 11 species of Penicillium were isolated from the indoor air while nine species were isolated from the air outside the homes. The dominant species of Penicillium in indoor as well as outdoor air were P. citrinum (33.78 and 32.81), P. oxalicum (19.70 and 22.60), and P. chrysogenum (17.64 and 14.50). The percentage of the Penicillium in the indoor air was 10.70 while it was 8.36 in outdoor air. Indoor air showed the presence of P. glaber and P. sclerotiorum, which were absent in the outdoor air.     

海河流域土壤中磷的库存量与通量研究

本通过对河流域土壤中磷及其形态含量的分析结果,计算出该流域土壤中磷的库存量为６．４２×１０＾１０ｋｇ。并以成土母质,人畜粪,化肥施入量和径流带入量,大气降尘及植物的残留量等因素为对土壤中磷的贡献,同时以径流的带出,大气的飘尘及植物体茎叶等因素为磷的迁出部分,计算出海流域土体中磷的进出量分别为４．２４×１０＾８ｋｇ／ａ和３．６６×１０＾８ｋｇ／ｄ,以此来研究其通量关系。     

Elevated Concentrations of Pesticides and PCBs in Soils at the Southern Caspian Sea (Iran) are Related to Land Use

Soil contamination by organochlorine pesticides or PCBs is almost undocumented for Iran. Here we report a soil survey in Mazandaran and Guilan provinces that hold >30% of the agricultural areas of Iran where pesticide use is widespread. Concentration of DDTs, HCHs, cyclodienes, and PCBs were measured in 45 soil samples from different agricultural land uses and forest land. The average concentrations of ∑DDT (37 μg kg^?1) and ∑HCH (21 μg kg^?1) in agricultural soils are among the largest ever reported and exceed international soil screening standards. All residues were larger in agricultural than in forest soil. Within agricultural land, ∑DDT were largest for tea gardens, lindane was largest in rice fields, and cyclodiens largest in citrus orchards. The ratio of (DDD + DDE)/DDT is an index of the extent of DDT degradation in soil and was lower in tea gardens than in other soils (0.7 versus 2–5), indicating either ongoing DDT input or lower degradation rate in the tea gardens that are more acid than the other soils (pH 4.5 versus 6.5–7.0). The o,p′–DDT/p,p′–DDT ratio was about 3 in forest soils, suggesting that DDT is derived from dicofol application and not from technical DDT as in agricultural soils. The PCB 28, 180, and 138 showed the highest mean concentration compared with other PCB congeners in all land uses. This survey is the first of this kind for Iran and illustrates that concentrations of organochlorine pesticide in soil are relatively large.     

Probabilistic Estimates of Lifetime Daily Doses from Consumption of Drinking Water Containing Trace Levels of N,N-diethyl-meta-toluamide (DEET), Triclosan,or Acetaminophen and the Associated Risk to Human Health

Risk assessments were conducted for N,N-diethyl-meta-toluamide (DEET), triclosan, and acetaminophen to evaluate the risk from exposure to trace levels of these chemicals through drinking water consumption. We estimated exposure to these chemicals through drinking water consumption by generating distributions for key exposure parameters using Monte Carlo analysis. Body weight and water consumption was modeled using data from the U.S. Environmental Protection Agency (USEPA) Exposure Factor Handbook. Water concentrations were derived from reported concentrations in streams. Dose-response was evaluated through extensive literature searches for toxicology data for each chemical. Acceptable daily intakes (ADIs) were then derived from the available toxicology data. The exposure distributions were compared to the ADIs to evaluate the potential risk to the population from drinking water exposure. ADIs of 0.100, 0.153, and 0.05 mg/kg-day were derived for DEET, acetaminophen and triclosan, respectively. The maximum estimated exposures (0.082, 0.834, and 0.193 μ g/kg/day for DEET, acetaminophen, and triclosan, respectively) were at least 100-fold lower than the corresponding ADIs. Based on these assessments, we conclude that there is minimal risk to human health from exposure to these chemicals at the reported concentrations in U.S. streams.