Central Tendency Exposure Research Articles

Assessment of Non-cancerous Health Risk from Exposure to Hg, As and Cd by Resident Children and Adults in Nangodi in the Upper East Region, Ghana

This study assessed non-cancerous health risk from exposure to mercury, arsenic and cadmium via oral ingestion of contaminated water bodies by resident children and adults in Nangodi, Upper East region, Ghana in accordance with US Environmental Protection Agency (USEPA). The mean concentration of arsenic, mercury and cadmium in water bodies in the study area for arsenic ranges from 0.0120 to 0.0653 mg/L; 0.0048 to 0.202 mg/L for mercury and 0.2665 to 1.090 mg/L for cadmium. These mean levels of arsenic, mercury and cadmium in water bodies from the study area were used as input parameters in calculating the non-cancerous health risk. The results of the non-cancerous health risk faced by resident children in the study area from exposure to mercury in a dug-well at Nakpadana is 6.7 via central tendency exposure parameter (CTE) and 13.0 via high end exposure parameter (HEE); in the case of arsenic we have 1.9 by CTE parameters and 3.7 by HEE parameters respectively, whilst for cadmium we had 29.0 and 58.0 by CTE and HEE parameters respectively. The non-cancerous health risk results expressed in terms of hazard quotient obtained in this study for both resident children and adults in most cases exceeded the acceptable USEPA hazard quotient value of 1.0, which suggests that resident adults and children are at high risk of showing symptoms associated with non-cancerous effects of exposure to arsenic, mercury and cadmium such as low IQ, tremor, renal failure, etc.

일부 공단지역 PM2.5에 부착된 중금속 노출에 의한 건강위해성평가

This study estimated the health risk of heavy metals in particulate matter <TEX>$(PM)_{2.5}$</TEX> in a Gwangyang industrial complex. The <TEX>$PM_{2.5}$</TEX> containing heavy metal was collected from January to November, 2008 using a denuder air sampler and by IC (Ion Chromatograph). The risk assessment was performed in a four-step process; hazard identification, exposure assessment, dose-response assessment and risk characterization. In the hazard identification process, <TEX>$Cr^{6+}$</TEX>, Ni, As, and Pb were categorized as human carcinogens and probable human carcinogens, while Ti, Mn, Se, P, <TEX>$Cr^{3+}$</TEX>, Cu, and Zn were not classified as human carcinogens. It was found that the excess cancer risk by Central Tendency Exposure (CTE) of <TEX>$Cr^{6+}$</TEX> and As in <TEX>$PM_{2.5}$</TEX> was > <TEX>$10^{-6}$</TEX>, and the total excess cancer risk posed by carcinogen heavy metals in <TEX>$PM_{2.5}$</TEX> was > <TEX>$10^{-6}$</TEX>. It was also determined that the total hazard index by CTE of non-carcinogen heavy metals in <TEX>$PM_{2.5}$</TEX> was <1. Taken together, these results indicate a high cancer risk associated whit inhalation of heavy metal-containing<TEX>$PM_{2.5}$</TEX> in industrial areas.

Cancer and Non-Cancer Risk Assessment from Exposure to Arsenic, Copper, and Cadmium in Borehole, Tap, and Surface Water in the Obuasi Municipality, Ghana

ABSTRACT Cancer and non-cancer risk assessment from exposure to As, Cd, and Cu by resident adults and children from different water sources in Obuasi Municipality, Ghana, were measured in this study in accordance with the U.S. Environmental Protection Agency's (USEPA's) Human Health Risk Assessment guidelines. The results of cancer health risk for resident adults in Obuasi exposed to As in their tap water for both Central Tendency Exposure (CTE) and Reasonable Maximum Exposure (RME) parameters, respectively, are 6.6 × 10−4 and 5.5 × 10−6. For resident children in Odumasi, we obtained 4.7 × 10−1 (CTE) and 6.7 × 10−1 (RME). The results of the study obtained in most cases were found to exceed the USEPA's acceptable cancer risk range of 1 × 10−6 to 1 × 10−4 (i.e., 1 case of cancer out of 1,000,000 people to 1 case of cancer out of 10,000 people). Similarly, the results of the non-cancer human health risk for both resident adults and children were also found in most cases to be greater than the USEPA's acceptable non-cancer human health hazard index of 1.

Evaluation of lead and mercury neurotoxic health risk by resident children in the Obuasi municipality, Ghana

This study assesses neurotoxic effects associated with exposure to lead and mercury in borehole, tap and surface water by resident children in the Obuasi municipality in accordance with USEPA risk assessment guidelines. From the results of the study, the hazard quotient for oral ingestion of mercury in tap water in Obuasi is 7.4 and 15 respectively via both central tendency exposure (CTE) and reasonable maximum exposure (RME) parameters, respectively. This means that approximately 7 and 15 (by both CTE and RME parameters, respectively) resident children in Obuasi are likely to show neurologic effects associated with exposure to mercury and lead such as increased nervousness, loss of memory and/or decrease in concentration, impaired writing ability and tremor.

Particle size fractionation and human exposure of polybrominated diphenyl ethers in indoor dust from Chicago

The objective of this study was to investigate the concentration level, the mass distribution based on dust particle size, and the associated human exposure of polybrominated diphenyl ethers (PBDEs) in indoor dust. The total concentration of 13 PBDEs Σ13(BDEs) was found to be 500–6,944 ng/g in indoor dusts, 4,000 ng/g in car interior dust, 260–300 ng/g in outdoor ambient air particles, 30 ng/g in carpet fibers, and as high as 0.5% in carpet padding. Selected dust samples were fractionated based on particle size, and over 80% of the Σ13BDEs were associated with particles < 150 μm in diameter. Mass ratios of BDE206/BDE209 are higher in both indoor and outdoor samples than in commercial deca products; and mass ratio BDE47/BDEs(85+99+100) was much higher in outdoor than in indoor samples. Using EPA software ProUCL, the exposure of Americans to PBDEs via hand-to-mouth transfer of house dust was estimated under the central tendency exposure and reasonable maximum exposure scenarios. The results suggest that ingestion of PBDE-laden house dust via hand-to-mouth contact is likely a significant exposure pathway, especially for children.

유아교육시설 내 실내공기유해오염물질에 대한 어린이 건강위해성평가

In this study, the hazard rate of the indoor environment of Children's Educational Facilities in Seoul was conducted, in order to determine how the indoor environments of these facilities, where infants and children spend the most time of their away from home day, can effect their health. The way of measurement and analysis were done according to the Indoor Air Quality Standard Method, and the Risk Assessment was accomplished with several significant ways - Hazard Identification, Exposure Assessment, Dose-response Assessment, Risk Characterization, which are deighed by National Research Council (NRC). On each exposure factors, documentary and questionary research such as Epidemiological study and Toxicological study were conducted. The result of the CTE (Central tendency exposure) of Formaldehyde and Benzene by Monte-Carlo simulation was <TEX>$6.79{\times}10^{-6}$</TEX>, <TEX>$2.50{\times}10^{-7}$</TEX> which in the case of Formaldehyde exceeded the permitted standard (<TEX>$10^{-6}$</TEX>) of the US EPA. The RME(Reasonable maximum exposure) was <TEX>$7.31{\times}10^{-5}$</TEX>, <TEX>$2.65{\times}10^{-6}$</TEX> which did not exceed <TEX>$10^{-4}$</TEX>, the maximum permitted standards in the US EPA.

Risk assessment before and after solar photocatalytic degradation of BTEX contaminated groundwater at a gas station site in Korea

AbstractWe assessed the incremental lifetime risks due to groundwater contamination with benzene, toluene, ethylbenzene, and xylene compounds (BTEX) for residents living on the site of a former gas station. Five remedial processes were applied to examine the degradation pattern of groundwater samples under similar weather conditions in winter: H2O2/solar light (action 1), immobilized TiO2/solar light (action 2), TiO2 slurry/solar light (action 3), immobilized TiO2/solar light/H2O2 (action 4), and TiO2 slurry/solar light/H2O2 (action 5). None of the remedial actions satisfied the criteria of acceptable risk (1 × 10−6 for carcinogens) using point estimation with both central tendency exposure (CTE) and reasonable maximum exposure (RME) for all pathways via designated exposure scenarios. Regarding the total hazard index (HI) for noncarcinogens, only action 5 satisfied all the exposure scenarios, both CTE and RME, for toluene, ethylbenzene, and xylene compounds, whereas the total health risk for benzene was between 10−5 and 10−6 for carcinogens. Results of probabilistic estimation before and after the treatment of benzene with action 5 using a Monte Carlo simulation were 68.1% for males (95% CI: 5.0 × 10−7 to 3.9 × 10−6) and 74.2% for females (95% CI: 5.0 × 10−7 to 4.6 × 10−6), exceeding the criteria of acceptable risk (10−6 for carcinogens). However, no adverse health risk was posed if remedial action 5 or an increased reaction time were applied. This study is a new attempt to integrate issues of groundwater contamination based on concentration and health risk assessment associated with different ex situ remedial actions. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Estimates of Hourly Dust and Soil Ingestion Rates for Children and Adults In- and Outdoors

ISEE-217 Objective: Daily soil and dust ingestion rates are often estimated using tracer studies. Information on the contribution of dust in the total soil and dust ingestion is often lacking. However, in view of the large contribution of indoor contaminants in the total exposure, this information is essential. Therefore, a mathematical model was developed that uses estimates of daily soil and dust ingestion rates from tracer studies, the fractions spend in- and outdoors and the indoor/outdoor ingestion ratio as input variables. Material and Methods: The average (±SD) daily soil and dust ingestion rates calculated from published tracer studies ranged between 71.8 ± 12.01 and 41.67 ± 10.32 mg/d for children and adults, respectively. For the Monte-Carlo simulations (5000 iterations) soil and dust ingestion was assumed to be log-normally distributed. The indoor/outdoor ingestion ratio was assumed to be uniformly distributed between 0.1 and 1.0 for children and between 0.3 and 1.0 for adults. A triangular distribution between 1 and 6 hours, with a most likely value of 3 hours was chosen for the time spent outside, both for children and adults. Results: Average hourly soil ingestion rates [corresponding with a central tendency exposure scenario (CTE)] for children outdoors and indoors of 13.55 and 3.28 mg/h were calculated. The average hourly dust ingestion inside was estimated as 3.44 mg/h. Corresponding estimates under a reasonable maximal exposure scenario (RME = 95th percentiles from simulations) for soil outdoors, indoors, and dust indoors were 22.52, 5.48, and 6.94 mg/h, respectively. For adults, these values were 5.78 (soil outdoors), 1.78 (soil indoors), and 1.90 mg/h (dust indoors) under a CTE scenario and 12.94 (soil outdoors), 3.83 (soil indoors), and 4.69 mg/h (dust indoors) under an RME scenario. Conclusions: Hourly ingestion rates for soil and dust allow the risk assessor to predict exposure to soil-borne pollutants for a particular setting and duration, more accurately.

Cancer and Non-Cancer Health Risk from Eating Cassava Grown in Some Mining Communities in Ghana

Food crops such as cassava, cocoyam and other tuber crops grown in mining communities uptake toxic or hazardous chemicals such as arsenic, and cadmium, from the soil. Cassava is a stable food for Ghanaians. This study evaluated human health risk from eating cassava grown in some mining communities in Ghana such as Bogoso, Prestea, Tarkwa and Tamso, which are important mining towns in the Western Region of Ghana. The study evaluated cancer and non-cancer health effects from eating cassava grown in the study areas in accordance with US Environmental Protection Agency's Risk Assessment guidelines. The results of the study revealed the following: cancer health risk for Tamso, 0.098 (RME--Reasonable Maximum Exposure) and 0.082 (CTE--Central Tendency Exposure). This means that approximately 10 and 8 out of 100 resident adults are likely to suffer from cancer related cases by RME and CTE parameters respectively. For Prestea, we have 0.010 and 0.12, which also means that approximately 1 out of 100 and 10 resident adults out of 100 are also likely to suffer from cancer related diseases by RME and CTE parameters. The results of the study obtained were found to be above the acceptable cancer risk range of 1x 10(-6) to 1x 10(-4), i.e., 1 case of cancer out of 1 million or 100,000 people respectively.

Non-Cancer Health Risk Assessment from Exposure to Cyanide by Resident Adults from the Mining Operations of Bogoso Gold Limited in Ghana

Cyanide is a very toxic chemical that is used to extract gold from its ores. Wastewaters from gold mining companies such as Bogoso Gold Limited (BGL) contain cyanide and other potentially toxic chemicals that have adverse effects on human beings and aquatic organisms. This study was conducted to evaluate the human health risk assessment from exposure to free cyanide via oral and dermal contact of surface/underground water by resident adults within the concession of Bogoso Gold Limited. The chronic non-cancer health risk from exposure to cyanide in River Bogo Upstream is 230 and 43 (by Central Tendency Exposure (CTE) parameters respectively). This means that approximately 230 and 43 resident adults are likely to suffer diseases related to cyanide intoxication via oral and dermal contact respectively. For chronic exposure to River Bogo Downstream by resident adults, the non-cancer health risks are: 0.031 and 0.57 via oral and dermal contact for CTE parameters respectively, which also means that, the non-cancer health risks associated with cyanide intoxication is negligible as the hazard index is less than 1.0 via oral and dermal contacts respectively. The results showed that health risk for acute exposure to cyanide by the resident adults is very high. Hence the residents attribute most of the unexplained deaths in the communities to accidental ingestion and dermal contact of cyanide water.

A Quantitative Look at Fluorosis, Fluoride Exposure, and Intake in Children Using a Health Risk Assessment Approach

The prevalence of dental fluorosis in the United States has increased during the last 30 years. In this study, we used a mathematical model commonly employed by the U.S. Environmental Protection Agency to estimate average daily intake of fluoride via all applicable exposure pathways contributing to fluorosis risk for infants and children living in hypothetical fluoridated and non-fluoridated communities. We also estimated hazard quotients for each exposure pathway and hazard indices for exposure conditions representative of central tendency exposure (CTE) and reasonable maximum exposure (RME) conditions. The exposure pathways considered were uptake of fluoride via fluoridated drinking water, beverages, cow’s milk, foods, and fluoride supplements for both age groups. Additionally, consumption of infant formula for infants and inadvertent swallowing of toothpaste while brushing and incidental ingestion of soil for children were also considered. The cumulative daily fluoride intake in fluoridated areas was estimated as 0.20 and 0.11 mg/kg-day for RME and CTE scenarios, respectively, for infants. On the other hand, the RME and CTE estimates for children were 0.23 and 0.06 mg/kg-day, respectively. In areas where municipal water is not fluoridated, our RME and CTE estimates for cumulative daily average intake were, respectively, 0.11 and 0.08 mg/kg-day for infants and 0.21 and 0.06 mg/kg-day for children. Our theoretical estimates are in good agreement with measurement-based estimates reported in the literature. Although CTE estimates were within the optimum range for dental caries prevention, the RME estimates were above the upper tolerable intake limit. This suggests that some children may be at risk for fluorosis.

Site-specific data confirm arsenic exposure predicted by the U.S. Environmental Protection Agency.

The EPA uses an exposure assessment model to estimate daily intake to chemicals of potential concern. At the Anaconda Superfund site in Montana, the EPA exposure assessment model was used to predict total and speciated urinary arsenic concentrations. Predicted concentrations were then compared to concentrations measured in children living near the site. When site-specific information on concentrations of arsenic in soil, interior dust, and diet, site-specific ingestion rates, and arsenic absorption rates were used, measured and predicted urinary arsenic concentrations were in reasonable agreement. The central tendency exposure assessment model successfully described the measured urinary arsenic concentration for the majority of children at the site. The reasonable maximum exposure assessment model successfully identified the uppermost exposed population. While the agreement between measured and predicted urinary arsenic is good, it is not exact. The variables that were identified which influenced agreement included soil and dust sample collection methodology, daily urinary volume, soil ingestion rate, and the ability to define the exposure unit. The concentration of arsenic in food affected agreement between measured and predicted total urinary arsenic, but was not considered when comparing measured and predicted speciated urinary arsenic. Speciated urinary arsenic is the recommended biomarker for recent inorganic arsenic exposure. By using site-specific data in the exposure assessment model, predicted risks from exposure to arsenic were less than predicted risks would have been if the EPA's default values had been used in the exposure assessment model. This difference resulted in reduced magnitude and cost of remediation while still protecting human health.