Human Health Risk Assessment Research Articles

Improving the integration of epidemiological data into human health risk assessment: What risk assessors told us they want

One of the practical contributions of epidemiology studies is to inform risk assessment and management to protect public health. However, there is a perception among some that environmental and occupational epidemiology is falling short of satisfying the needs of risk assessors. The specific reasons for this are not clearly understood. To help identify the points of dissatisfaction and possible areas for mutual learning, we conducted a survey of risk assessors, seeking their opinions of epidemiology research. We present a few quantitative measures and a thematic analysis of responses to open-ended questions. Survey results suggest that some risk assessors (with some adamant exceptions) believe that epidemiology has great potential to contribute to risk assessment but can be deficient in many ways. For example, respondents identified the lack of full disclosure of methods, deficiencies in exposure assessment, the absence of comprehensive uncertainty analyses, and the failure to investigate or explore thresholds of effects as some of the common shortcomings. These could be straightforward to address. Respondents also brought up a wide collection of more complicated and subtle concerns that could lead to further improvement of useful results. We identify areas where mutually-educating interdisciplinary dialogue seems particularly promising. Epidemiology research is expensive, and risk management decisions even more so; therefore, it is desirable for the risk assessment and epidemiologic communities to work toward making epidemiologic research more useful for informing decisions.

Quantification of Micro and Trace Elements in Tobacco Products Using Total Reflection X‐Ray Fluorescence Spectrometry: A Human Health Risk Assessment

Quantification of Micro and Trace Elements in Tobacco Products Using Total Reflection X‐Ray Fluorescence Spectrometry: A Human Health Risk Assessment

Incorporating source apportionment and health risk assessment of heavy metals from indoor dust of an industrial area in Dhaka, Bangladesh

A total of 45 deposited dust samples were collected from the preselected 15 households near an industrial area at Savar, Bangladesh. The concentrations of metals were measured by EDXRF spectroscopy and was found at the following trend: Ca > Fe > K > Ti > Mn > Zr > Sr > Rb > Zn > Cu > Pb > Co. The average concentrations of Cu, Zn, Zr, and Pb were found to be higher than that of the soil background values set by Chinese Environmental Protection Administration (CEPA) and the upper continental crust (UCC), while the average concentrations of K, Ti, Fe, and Rb were found to be higher than that of the background values and lower than that of UCC. Alternately, %RSD for some toxic metals (i.e., Fe, Co, Zn and Pb) in the dust samples were ranged broadly (%RSD: 33.54–86.88 %), which indicates that these trace metals might be present in indoor dust samples due to anthropogenic sources, which is consistent with the ANOVA test. In this study, the contamination levels of metals were assessed based on the enrichment factor (EF), pollution load index (PLI), and geo-accumulation index (Igeo). The two ways ANOVA (Fcal = 3.86 >Fcritic = 1.78, df = 14) for EF data had revealed the heterogeneity of metal enrichment in the study area, whereas PLI values were close to 1.0 or > 1, which indicated that the indoor dust samples in the study area might be deteriorated of site quality by the studied metals. The analysis of Igeo also revealed that these dust samples are slightly to extremely polluted. Conversely Pearson correlation analysis, principal component analysis, and cluster analysis were employed to identify the possible sources of such heavy metals, which suggested that the anthropogenic sources are the main sources of the examined heavy elements. Subsequently, the human health risk assessment strategies were applied to identify the routes of exposures based on the US EPA health risk models. For non-cancer effect, ingestion of dust particles is the main exposure route to both the children and adults. The total hazard index (HI) values indicate that both children and adults are vulnerable to non-carcinogenic effect, but children are more vulnerable than adults (tstat = 1.97 >tcritic = 2.039, p = 0.029) at a 95 % confidence level. Nevertheless, no significant carcinogenic health risk due to the presence of Co was found for both children and adults in the study area. According to sensitivity analysis, the ingestion rate (IR) and the concentration of Co posed the most significant impact (> 79.9 %) on cancer risk estimation.

Preliminary human health risk assessment of antibiotic exposures in human waste handling occupations

Exposure to biosolids in human waste handling occupations is associated with a risk for illness due to microbial infections. Although several years of exposure to biosolids might be hypothesized to be a prophylaxis against infection, the risks associated with infections from antibiotic-resistant organisms can also be a potential concern. Therefore, this study aimed to conduct a screening level risk assessment by deriving occupational exposure limits (OELs) characterizing the risks of adverse health effects among workers in human waste handling occupations with a focus on exposure to two pharmaceuticals commonly found in biosolids: ciprofloxacin (CIP) and azithromycin (AZ). Epidemiological and exposure studies of workers exposed to biosolids were identified through searches of major scientific databases. Screening OELs (sOELs) for these antibiotics were derived using a standardized methodology. The airborne concentrations of CIP and AZ antibiotics were determined using an exposure factors approach. The health-based exposure limits (i.e., sOELs) and the acceptable daily exposure (ADE) values for both of these antibiotics were derived as 80 μg/m3 and 12 μg/kg-day, respectively. An exposure factor approach suggested that inhalation route exposures to CIP and AZ are well below the sOELs and ADE daily doses, and likely too low to cause direct adverse health effects through antibiotic inhalation. A critical review of epidemiological studies on different occupations handling biosolids showed that the workers in industries with potential biosolids exposure have experienced an increased incidence of microbial-exposure-related illness. The health effects seen in the workers have been attributed to bacterial, viral, and protozoan infections. To the extent that bacteria are the pathogen of concern, it is not clear whether these bacteria are resistant to antibiotics commonly found in biosolids. It is also unclear whether the presence of antibiotics or antibiotic-resistant bacteria increases the susceptibility of these workers. Additional studies will provide more definitive estimates of inhalation and dermal exposures to CIP and AZ and could verify the exposure estimates in this study based on the literature and common exposure factors.

Source-specific ecological and human health risk analysis of topsoil heavy metals in urban greenspace: a case study from Tianshui City, northwest China.

Soil contamination of heavy metals in urban greenspaces can exert detrimental impacts on ecological biodiversity and the health of inhabitants through cross-media migration-induced risks. Here, a total of 72 topsoil samples were collected from greenspaces in the popular tourist city of Tianshui, ranging from areas with parks, residential, road, industrial and educational soils. The study aimed to evaluate an integrated source-specific ecological and human health risk assessment of heavy metals. Among the analyzed heavy metals, except Cr (mean), all exceeded the local background values by 1.30-5.67-fold, and Hg, Cd, Pb and As were the metals with large CV values. The Igeo and CF results showed Hg, Cd, As and Pb exhibited significantly high pollution levels and were the primary pollution factors. The mean PLI values indicated moderate pollution in educational (2.21), industrial (2.07), and road (2.02) soils but slight pollution in park (1.84) and residential (1.39) greenspaces. The Igeo, CF, and PLI results also revealing that these heavy metals are more likely to be affected by human activity. Four primary source factors were identified based on PMF model: coal combustion (25.57%), agricultural sources (14.49%), atmospheric deposition (20.44%) and mixed sources (39.50%). In terms of ecological risk, the mean IRI values showed considerable risks in educational soils (287.52) and moderate risks in road (215.09), park (151.27) and residential (136.71) soils. And the contribution ratio of atmospheric deposition for park, residential, road, industrial and educational greenspaces were 57.72%, 65.41%, 67.69%, 59.60% and 75.76%, respectively. In terms of human health risk, the HI (below 1) and CR (below 1.00E-04) for adults from soils of all land use types was negligible. However, children have more significant non-carcinogenic and carcinogenic hazards especially in residential soils, the HI (above 1) and CR (above 1.00E-04) revealed the significance of regarding legacy As contamination from coal combustion when formulating risk mitigation strategies in this area. The proposed method for source and risk identification makes the multifaceted concerns of pollution and the different relevant risks into a concrete decision-making process, providing robust support for soil contamination control.

Hydrochemical insights, water quality, and human health risk assessment of groundwater in a coastal area of southeastern China.

Groundwater is a vital water supply worldwide, but its quality has gradually deteriorated with the development of society. In this study, a total of 40 groundwater samples were collected during the pre- and post-monsoon to analyze the hydrochemical process and assess the groundwater quality and human health risks in a coastal area of southeastern China. The results showed that the concentrations of major ions were in the order of Ca2+> Mg2+ > Na+ > K+ and HCO3- > SO42- > Cl- > NO3- > F- during the pre- and post-monsoon periods. A slight increase was observed during the post-monsoon period. The Piper diagram suggested that the hydrochemical type of groundwater was predominantly HCO3-Ca. Principal component analysis (PCA), ionic ratios, and saturation index (SI) determined that the water-rock interactions involving silicate and carbonate minerals played a significant role in the hydrochemical process. The results of the entropy-weighted water quality index (EWQI) and irrigation water quality index (IWQI) evaluations revealed that the general qualities of groundwater were suitable for both drinking and irrigation purposes. However, the excesses of NO3- and SO42- were observed locally. Human health risk assessment concluded that groundwater posed a low risk to human health, and infants faced higher risk compared with adults. The study would provide valuable information for groundwater environmental protection.

Dermal Exposure to Alkylphenol Ethoxylates in As-Purchased Garments: Human Health Risk Assessment

Textile production involves using various chemicals that may remain in clothing and pose health risks. Alkylphenol ethoxylates are non-ionic surfactants which may be involved in various textile printing and dyeing auxiliaries due to their excellent emulsification, wetting and decontamination abilities. This study aimed to determine the dermal exposure doses and health risks of alkylphenol ethoxylates in 10 unwashed textile samples for infants, toddlers and pregnant women. The concentrations of alkylphenol ethoxylates and alkylphenols (APs) were determined by liquid chromatography–mass spectrometry (LC-MS/MS). The total concentrations of alkylphenol ethoxylates (nonylphenol ethoxylates and octylphenol ethoxylates) in 10 textile samples were 113.21–1431.18 mg/kg, among which nonylphenol ethoxylates with ethoxy groups of 2–10 were the dominant chemicals. The highest dermal exposure dose was found in the toddler group, which was 1.27 and 4.14 times higher than those in the infant and pregnant women groups. When the maximum concentration was used for risk assessment based on tolerable daily intake, the hazard indices ( HI) for toddlers and infants were estimated to be 10.62 and 8.37, which may pose a higher risk to human health. Our assessment was specifically focused on new garments before washing. The garments containing alkylphenol ethoxylates can be washed to significantly reduce the exposure risk. The results of our study offer important information on human exposure to alkylphenol ethoxylates in textiles and clothing and provide a scientific basis for planning risk management measures for alkylphenol ethoxylates.

Assessment of potentially toxic element contamination in commercially harvested invertebrates from the Beibu Gulf, China

Marine pollutants, especially potentially toxic elements (PTEs), increasingly threaten the ecological environment and fishery resources of the Beibu Gulf due to their bioaccumulative nature, toxicity, and persistence. However, the occurrences of multiple PTEs in marine invertebrates within this region remains unclear. Hence, a total of 18 species of commercially harvested invertebrates (shrimp, crab, cephalopod, shellfish, and sea cucumber) were collected from the Beibu Gulf, and the concentrations of nine important PTEs (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were examined. Subsequent stable isotope analysis for δ13C and δ15N facilitated investigations into biomagnification and human health risk assessment. The results showed that, except for As, the concentrations of the PTEs in the invertebrates were below the national safety limits. Furthermore, significant positive correlations were found between trophic levels (TLs) and log-transformed concentrations of As (P < 0.001, R2 = 0.20) and Cr (P < 0.001, R2 = 0.13), indicating biomagnification of these two metals across trophic positions among species. Finally, the human health risk assessment revealed that the consumption of cephalopod, shellfish, and sea cucumber poses a higher risk of adverse effects compared to shrimp and crab.

The human health risks assessment posed by the presence of heavy metals in the rice varieties available in the Neyshabur market.

The present study was designed to determine the levels of heavy metals (Cu, Pb, Ni, Cr, Zn, Mn, Cd, and Co), Mn, and As in Iranian-grown rice and imported rice consumed in Neyshabur City. For this research, 90 samples from 30 different brands widely consumed in this city were collected. The content of heavy metals and the health risks associated with their use were then studied. The study found that Zn (14.21mgkg-1) had the highest content in Iranian and imported rice varieties, whereas Cd (0.02mgkg-1) had the lowest value. The health risk assessment was also done in three scenarios and separately for two types of rice. The results showed that the total hazard quotient (i.e., THQ) was measured for all metals and all three scenarios, and for both types of rice, it is THQ > 1, which indicates the risk of non-carcinogenic in rice. The cancer risk for three scenarios and two types of imported andIranian rice is in the unsafe range for As (8.80× 10-4 to 7.00× 10-3),Ni (4.60 × 10-4 to 3.60 × 10-3) and Cr (2.20 × 10-4 to 1.90 × 10-3) and negligible for Pb (1.09 × 10-6 to 1.49 × 10-5) and Cd (7.83 × 10-6 to 8.20 × 10-5).

Probabilistic human health risk assessment of commercially supplied jar water in Gopalganj municipal area, Bangladesh

Every day, the amount of quality fresh water decreases notably due to contamination of drinking water. As a result, people use commercially supplied jar water in the southern part of Bangladesh as well as in the Gopalganj municipal area. This study aims to investigate the physicochemical parameters, trace elements, and microbial parameters for assessing human health risks from oral ingestion of these elements. This study gathered commercially supplied jar water samples from 15 companies in the Gopalganj municipal area during the post-monsoon season. Temperature, potential of hydrogen (pH), total dissolved solids (TDS), electrical conductivity (EC), and salinity showed significant variation among the samples, and the level was within the national and international standard limits. The concentrations of iron (Fe) and arsenic (As) were measured using a UV–VIS spectrophotometer and atomic absorption spectroscopy (AAS), respectively. The microbial analysis was conducted by the membrane filtration method. The study found that the water samples had an average concentration of 0.16 mg/L in terms of Fe and 0.016 mg/L in terms of As, with the mean value of As exceeding the standard limits. On the other hand, the mean Fe concentration value did not exceed the standards. Probable human health risk from heavy metal in the jar water was determined by hazard quotient (HQ), hazard index (HI), and carcinogenic risk (CR) assessments. A child (HI = 3.5914) is more vulnerable to non-carcinogenic human health risks than an adult (HI = 1.6931). Furthermore, pollution in water samples was found to pose a high carcinogenic risk, with children (CR = 1.6 × 10−3) being more vulnerable to carcinogenic risk than adults (CR = 7.5 × 10−4). In the microbial analysis, 100% of the samples exceeded the total coliform and fecal coliform standard limits, and 80% of the samples exceeded the Escherichia coli standard limits. Among the samples, 7% present high risk, around 47% present medium risk, 26% show low risk, and 20% show no risk based on the E. coli standard limits. This study did not find any samples that exceeded the extremely high limit for E. coli concentration. This study found that drinking jar water samples had inadequate quality, which may increase the risk of water-borne infections such diarrhea as well as heart disease, diabetes, and cancer. As a result, the manufacturer of drinking water in jars must carry out the essential quality control procedures, and the government should regularly monitor the procedures.

Human health risk assessment of heavy metals in residential soil-Houston, Texas.

Human health risk assessment increasingly recognizes the need to integrate participatory-based research, geospatial analysis, and environmental epidemiology, particularly to address contamination concerns in underserved and disadvantaged communities. Here, we demonstrate the combined application of such methods within the Greater Fifth Ward neighborhood in Northeast Houston. In particular, in tandem with community members, we collected soil samples from 193 residential sites using a complete canvassing method from July to November 2021 to characterize contaminant concentrations, focusing on heavy metals and metalloids As, Ba, Cd, Cr, Pb, Se, Ag, and Hg measured using Inductively Coupled Plasma-Mass Spectrometry. Individual heavy metals as well as cumulative cancer and non-cancer risks were calculated for children and adults using the USEPA Regional Soil Screening Levels and benchmarks for specific land uses, such as crop growing. Soils from most sites had low or typical background levels expected in urban areas, but samples from several locations had significantly elevated lead levels (>1200 mg/kg) that warrant additional examination. Geospatial analysis suggested clustering of heavy metal contaminants within one geographic area of the neighborhood. This study highlights how participatory research in underserved environmental justice communities can help characterize current conditions as well as establish priorities for future investigation.

Building knowledge of NAMs through risk science

The 12th World Congress on Alternatives and Animal Use in the Life Sciences provided a platform for mobilizing and exchanging knowledge on the advancements in science and technology. It also provided an opportunity for experts to discuss how to accelerate the adoption of new strategies and tools. One of these recommendations advocated the need to bridge the gap between the next generation of scientists who have yet to learn about ‘New Approach Methodologies’ (NAMs) and the current generation of thought leaders who have pioneered the development and validation of these non-animal approaches to toxicological risk assessment. Consequently, a mini-course, held at Canada's University of Ottawa, was developed for students, aged 13–16 years, interested in learning about risk science and how NAMs can be used to inform human health risk assessment. This course also served as a platform for creating a virtual training roadmap, provided in this paper, thereby bringing this knowledge to a broader audience of learners who are establishing their careers in the field of risk science.

Human health risk assessment of trace metals and metalloids concentrations in saffron grown in Gonabad, Iran

Trace metals and metalloids are environmental contaminants that in elevated levels they may pose serious threats to human health. The aim of this research was to investigate trace metals and metalloids contamination in saffron grown in Gonabad. Potential health risks associated with the consumption of this product were also estimated. Totally, 48 samples were collected from 16 saffron farms. Then, the samples were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-OES) technique. For As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, the levels ranged between 0.01–0.36, 0.01–1.31, 0.01–0.28, 0.86–2.31, 4.98–42.04, 92.530–740.66, 14.80–26.28, 0.66–1.78, 0.07–0.84 and 24.32–56.71 mg/kg, respectively. However, levels of cadmium, iron and zinc were above the FAO/WHO limits in few samples. The results showed that all the samples had hazard quotient (HQ) values less than 1 for children, teenagers and adults, respectively, indicating that exposure to the elements via saffron consumption might not pose non-carcinogenic health risk. The estimated cancer risk among the studied groups were low and negligible, indicating that low probability of cancer development from long-term consumption of saffron.

Pharmaceuticals and personal care products and heavy metals in the Ganga River, India: Distribution, ecological and human health risk assessment

In the present study, pharmaceuticals and personal care products (PPCPs), endocrine disrupting compounds (EDCs), and heavy metals (HMs), were measured in water and sediment of the Ganga River during summer and winter seasons for two consecutive years. Additionally, this study estimated the ecological and human health risks associated with PPCPs, EDCs, and HMs. HMs detected in the range of not detected (n.d.) to 23.59 μg/L and 0.01–391.44 μg/g in water and sediment samples, respectively. All studied HMs were within the permissible limits, except for As in water, and Cr and Ni in sediment. The geo-accumulation index (Igeo) indicated that Cr (0.71–5.98) and Pb (0.90–3.90) had high Igeo compared to other metals in sediment samples. Pb showed the highest ecological risk, followed by Cd, Co, Ni, Cu, Cr, As, and Zn. The maximum potential ecological risk index was observed at site G8. The hazard index (HI) value for water (0.08–0.89) and sediment (0.02–0.29) intake by adults remained within the acceptable limits, except at sites G8 (1.27) and G9 (1.34) for water intake. However, for children, the HI value was above the acceptable limit for water intake at sites G4 to G13 and for sediment at site G8. Among the studied compounds, metformin, triclosan, triclocarban, diclofenac, and methylparaben were the most abundant compounds present in the Ganga River. PPCPs and EDCs detected in the range of n.d. to 5850.04 ng/L and n.d. to 1080.41 ng/g in water and sediment samples, respectively. The environmental risk assessment identifies the maximum ecological risk in water exhibited by triclocarban followed by 17α-ethinylestradiol (EE2), diclofenac, and triclosan, while in sediment, the maximum ecological risk exhibited by triclocarban, followed by EE2, 17 β-estradiol (E2), triclosan, and diclofenac. However, none of the compounds showed human health risk, except for EE2, E2, and atenolol.

Trace element concentrations and associated human health risk assessment in canned tuna, city of Neyshabur, Iran

Seafood is considered a healthy and nutritious food, but the presence of toxic substances in such foods is a serious problem. The present study aimed to analyze the concentration of some toxic metals in seafood and evaluate their noncarcinogenic risks to consumers. Samples were digested according to the Association of Official Agricultural Chemists (AOAC) standard. The heavy metals concentration of Cd, Ni, Hg, Pb, and Sn in 30 canned tuna samples were determined using an inductively coupled plasma optical emission spectroscopy (ICP-OES). The mean concentrations of Cd, Ni, Sn, Pb, and Hg were 0.7, 0.49, 1.03, 0.31, and 0.12 µg g− 1, respectively. Based on these results, the concentrations of Cd, Sn, and Hg in samples met the required standards. However, the concentrations of Ni and Pb in some samples were higher than the permissible limits. The mean values of Sn, Ni, Pb, Hg, and Cd in samples followed a decreasing order. Since the values of the health risk index for these samples were lower than the HI and HRI risk threshold (<1), they can be consumed without any problems arising. Highlights The metal concentration was measured in the four most popular brands of canned fish sold in Neyshabur City, Iran. Some samples exceeded the maximum permissible level of nickel (Ni) and lead (Pb). A significant correlation was observed between Ni concentration with Pb and Hg concentrations and Pb concentration with Cd concentration. The values of the health risk index (HRI) for noncarcinogenic health risks were lower than 1. The calculated Hazard index (HI) for adult and child consumers was less than 1. The HI values were greater for children than for adults.

Comprehensive risk assessment of lead concentrations in chicken, quail, and duck egg albumen and yolk using Monte Carlo simulations

This study conducted a comparative analysis of the concentration of the lead (Pb) in the albumen and yolk of eggs from domesticated chicken, quail, and duck, with a concurrent assessment of the potential carcinogenic and non-carcinogenic risks associated with the consumption of eggs sourced from Türkiye. A total of 78 poultry egg samples were gathered from breeding farms and farmers' markets situated in Şanlıurfa province. Lead concentrations were assessed through inductively coupled plasma optical emission spectrometry (ICP-OES). Human health risk assessment adheres to the guidelines set forth by the United States Environmental Protection Agency (US EPA), which primarily emphasizes estimated daily intake (EDI), international lifetime cancer risk (ILCR), target hazard quotient (THQ), and Monte Carlo simulation (MCS) as a probabilistic approach. One-way analysis of variance (ANOVA) was employed to compare Pb concentrations within egg yolks and albumens, as well as among various types of eggs. The levels of Pb found in the albumen of chicken, quail, and duck eggs were measured to be 0.31 ± 0.11, 0.43 ± 0.11, and 0.47 ± 0.16 μg kg−1, respectively. The concentrations of Pb in the yolks of chicken, quail, and duck eggs were found to be 0.54 ± 0.19, 0.28 ± 0.11, and 0.69 ± 0.21 μg kg−1, respectively. These concentrations were below the maximum permitted levels set by the FAO/WHO. The results indicated that Pb content in all tested eggs was safe for consumption, with exposure levels significantly below Joint FAO/WHO Expert Committee on Food Additives (JECFA) risk thresholds. The THQ values were less than one, indicating no non-carcinogenic risk. In addition, this study provides accurate and reliable data for policy makers to improve food safety measures and reduce potential public health risks.

Assessment of heavy metals and proximate composition in jellyfish (Lobonemoides robustus Stiasny, 1920) collected from Cox's Bazar coast: Human health risk assessment

Jellyfish are known for experiencing periodic blooms in population, which occur when their density increases suddenly. The present study assessed the level of heavy metals and proximate composition in the jellyfish Lobonemoides robustus collected from Cox's Bazar coast of Bangladesh. This is the first study conducted in Bangladesh. Most of the studied metals were not possible to detect in L. robustus samples because concentrations were below the detection limit. Ca, Na, Se, and Mg were found to have safe levels in the L. robustus while the amount of Pb was recorded 0.39 ppm. The findings of Target Hazard Quotient, and Carcinogenic Risk indicate that the L. robustus is safe for human consumption (both for children and adults). Hence, it is suitable for consumption and can be exported. This study emphasizes the need for regular marine environment monitoring to ensure that the seafood harvested from these waters is safe for consumption.

Human health risk and water quality assessment due to fluoride and nitrate around Cauvery River basin, southern India.

Good quality water for human consumption, irrigation, and industrial use is very important. Today, around the world, water is contaminated by natural processes and human activities. This study aimed to evaluate the suitability of groundwater for drinking and irrigation, identifythe source of fluoride and nitrate contamination, and assess thehuman health risks around the Cauvery River basin in southern India. A total of 30 groundwater samples were collected and analyzed for hydrochemical parameters, including EC, TDS, pH, Ca, Mg, Na, K, HCO3, Cl, SO4, NO3, and F-. The majority of groundwater samples in the study area are used for drinking and irrigation. The pH of groundwater in the study area was observed to be dominantly alkaline. The levels of TDS, Ca, Na, K, F, and TH exceeded the permissible limits recommended by BIS and WHO. Fluoride and nitrate levels in groundwater exceeded the permissible limits for drinking purposes in 43% and 50% of the samples, respectively. The excessive concentration of fluoride and nitrate in groundwater could pose serious human health problems. Fluoride and nitrate concentrations in groundwater vary between 0.1 and 2mg/l and 12 and 95mg/l, respectively. Based on the computation of the drinking water quality index, about 73% of groundwater samples were classified asexcellent to good. Health risk was assessed for infants, children, and adults using non-carcinogenic risk indices such as hazard quotients (HQ), hazard indexes (HI), total hazard indices (THI), and carcinogenic risk indices (CR). Infants, children, and adults have different total hazards indexes ranging from 1.508 to 5.733, 1.579 to 6.003, and 0.011 to 0.046, respectively. Health risk assessment results indicatedthat the hazard index and hazard quotient were above the recommended limit of > 1 in most of the samples for infants and children. Non-carcinogenic risk and carcinogenic risks were more likely to affect infants and children rather than adults through ingestion of contaminated water.

Nitrate Contamination in the Groundwater and Associated Human Health Risk Assessment for Gaya District, Bihar, India

The study pertains to nitrate concentration in groundwater resources of the Gaya district, Bihar, India and its related health risk to the local population. Groundwater serves as the principal source of drinking water in the area. 40 representative groundwater samples were collected and analyzed for nitrate and other water quality parameters. The concentration of Nitrate (NO3 -) in the groundwater of Gaya district varied from 1.62 to 155.6 mg/L and exceeded the Bureau of Indian Standards (BIS) permissible limits for drinking water in 30% of the samples. The elevated nitrate levels were predominantly attributed to agricultural activities. To evaluate the human health risks associated with groundwater, Hazard Quotient for nitrate (HQnitrate) were calculated using the United States Environmental Protection Agency method. The mean HQnitrate values were estimated to be 1.03, 0.89 and 1.65 for the male, female and child populace, respectively depicting considerable risk to male and child populace. In 67.5% of the samples, HQnitrate for children exceeded the safety threshold of 1. The study advocates significant health risks, especially to children in many parts of Gaya district due to high concentrations of nitrate in the groundwater. Judicial use of nitrogen-based fertilizers is suggested to prevent further contamination of groundwater.

The cliff-edge of toxicological concern: highlighting the potential issues of an over-reliance on "less-than-lifetime" thresholds.

The Threshold of Toxicological Concern (TTC) is a very well-established concept in applied toxicology, and has become a key tool for the pragmatic human health risk assessment of data-poor chemicals. Within the pharmaceutical sector, regulatory guidance on genotoxins defaults to a TTC of 1.5μg/day equating to a maximum lifetime cancer risk of 1 in 100,000. Higher doses for drug products where exposures are intermittent or otherwise "less-than-lifetime" (LTL) are also considered tolerable. This also allows substance-specific lifetime Acceptable Intakes (AIs) for known genotoxic carcinogens to be scaled up for shorter durations. The default TTCs for assessing LTL exposures build in conservatism such that there is deviation from strict linearity. However, close to the boundaries between LTL categories there can be such a difference in the default tolerable intakes that a health risk assessment can yield conflicting results. We have presented a theoretical case study based on our recent work that illustrates this apparent "cliff-edge." The total acceptable cumulative dose over a 56-day treatment is - in absolute terms - one third of that allowed over 28days, despite the maximum cancer risk of the longer exposure being an order of magnitude higher. Our analysis suggests the need for careful consideration of what might represent tolerable exposures in the region of the category limits, rather than simply adopting the hardline default. Where a potential patient exposure is found to be above a default value, there is real value in refining the cancer risk estimates using the Lifetime Cumulative Dose approach.