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Risk Characterization
Published in Ted W. Simon, Environmental Risk Assessment, 2019
For each chemical-producing systemic toxicity, the dose estimate is divided by the RfD to obtain a hazard quotient (Equation 6.1). If the hazard index is less than 1, the risk for that chemical is considered unlikely to lead to adverse health effects. If the hazard index is greater than 1, adverse health effects are more likely, and suggest that risk management should be considered. For multiple chemicals, hazard quotients can be summed to estimate an overall hazard index (HI). For exposure by the dermal route, the RfD is adjusted to reflect an absorbed dose, as detailed in Appendix A of EPA’s Risk Assessment Guidance for Superfund, Volume I, Part A.3,4For exposure by the inhalation route, the reference concentration (RfC) is used in lieu of the RfD.5
Overview of Approach to Noncancer Risk Assessment
Published in John C. Lipscomb, Edward V. Ohanian, Toxicokinetics and Risk Assessment, 2016
Several different approaches are used in risk characterizations for comparing the dose–response and exposure assessments, depending on the approach used for the dose–response assessment and the available data. A hazard quotient (HQ) is the ratio between the exposure and the RfD, RfC, or similar value typically derived in noncancer risk assessments. HQ values below 1 indicate that an effect is unlikely, while the probability of an effect, the percentage of people affected, and the severity of the risk usually increases as the HQ increases above 1. However, noncancer risk values such as RfDs or ADIs are generally imprecise, and small differences in the HQ in the region of 1 cannot be distinguished scientifically from a value of 1. The use of a bright-line cutoff is a policy decision and should not be interpreted as meaning that any HQ above 1 carries a risk while any HQ below 1 is safe for every individual. Any risk from small exceedances of the RfD or RfC will generally apply only to the most sensitive individuals in the population, and larger exceedances are generally required before the fraction of the population affected may increase. Conversely, while exposures at or below the RfD or RfC are considered protective for sensitive people for most chemicals, one cannot rule out the possibility that exposure at these levels may result in some small risk for highly sensitive individuals for some chemicals.
Human health risks in Ferozepur District, Punjab, India due to potentially toxic elements in agricultural soils
Published in Toxin Reviews, 2023
Inderpreet Kaur, Harpreet Kaur Dhillon, Sakshi Sharma
As per USEPA (1989) if values of hazard quotient (HQ) and Hazard index (HI) > 1, it indicates a high possibility of occurrence of non-carcinogenic health problems in residents of the study area. It was observed that only in case of children, mean value of HQing (1.20) and HI (1.30) for As was observed to >1, whereas the mean values of HQing (or HQinh or HQder or HI) for all other PTEs <1. In case of Adults, all mean HQ values estimated for three exposure pathways were < 1. These results suggested that children in the study area are more susceptible to non-cancer health risks due to exposure to As via ingestion as a dominating pathway. Moreover, Children are more prone to non-cancer health risk in comparison to adults, which may be attributed to their lower body weight.
Monitoring and health risk assessment of organochlorine pesticides in Karun River and drinking water Ahvaz city, South West of Iran
Published in Toxin Reviews, 2022
Sahand Jorfi, Ali Poormohammadi, Elham Maraghi, Halime Almasi
Life-time cancer risk (LCR) is used to estimate carcinogenicity. It is an indicator of the probability for increasing the incidence of cancer due to specific exposure (Equation (2)). In addition, the hazard ratio relationship is used to estimate the risk of non-carcinogenic exposure (Rahimnejad et al.2014). The relationship of the hazard quotient (HQ) is the ratio of exposure to a substance than that of the substance without any adverse effects (Rahimnejad et al.2014). The non-carcinogenic human health risks caused by the exposure to OCPs in Karun River are given as HQs (Table 3). Slope factor is an acceptable range where the probability of a response to the consumption of a chemical is present during the lifetime. The presence of pesticide residues in the water indicates an environmental and health risk due to its application for agricultural purposes. Hence, regular monitoring programs are required to assess the health risks in relation to such contaminants, especially chronic exposure due to the long-term consumption of contaminated drinking water (Ismail et al.2015). The entry of pesticides into drinking water sources due to their extreme resistance to environmental factors, water solubility and toxicity can pose adverse effects to the environment and human health. Various studies showed that the residues of pesticides in water resources are directly proportional to the amount of their consumption in these areas. Therefore, if these pesticides are not controlled, they can pose a serious threat to the health of consumers (Mendes et al.2019).
Distribution, source identification, ecological and health risks of heavy metals in surface sediments of the Rupsa River, Bangladesh
Published in Toxin Reviews, 2021
Ram Proshad, Tapos Kormoker, Saiful Islam
The potential noncarcinogenic risks for each individual heavy metal (Cr, Ni, Cu, As, Cd and Pb) through ingestion were assessed by the target hazard quotient (THQ) (USEPA 1989). The methodology for the estimation of noncarcinogenic risks was applied in accordance with that provided by the U.S. Environmental Protection Agency (USEPA) Region III’s risk-based concentration table (USEPA 2011). Hazard quotient (HQ) was determined on the basis of chronic daily intake from ingestion (CDIingest-sediment) and it was calculated by dividing the average daily dose to a specific reference dose (RfD) (USEPA 1989, Qu et al.2012, Genthe et al.2013). The equation used for estimating the target hazard quotient is as follows: 2002, USDOE 2011). The reference dose (RfD) (mg/kg/day) is an estimation of maximum permissible risk on human population through daily exposure, taking into consideration sensitive group (children) during the lifetime. If the CDI is higher than RfD (HQ > 1), there will be a severe health hazard to human, whereas CDI is less than RfD (HQ ≤ 1), there will be no severe human health effects (USEPA 1989, USEPA 2001b). The health risk guidelines determination of chemical mixtures defined that “simultaneous sub-threshold exposures to several chemicals may result in an adverse health effect” and “the magnitude of the adverse effect will be proportional to the sum of the ratios of the sub-threshold exposures to acceptable exposures” (USEPA 1986).