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Combined sewer overflows (CSOs) are a source of microbial contamination of drinking water intakes located downstream from their discharge. To safeguard the quality of the source water, it is essential to evaluate the risk levels associated with these municipal structures. This study compares two risk assessment approaches to test their applicability for assessing the risk of CSOs to drinking water intakes in a highly urbanized watershed. The first approach was based on a deterministic equation that combines the characteristics of an overflow structure allowing the risk to be rated as very low, low, medium, high, or very high. The second probabilistic risk assessment approach yielded findings that are probabilistically distributed across the five levels of risk. This approach was developed by constructing a novel Bayesian network to probabilistically link the different factors defining the exposure of water intakes to the hazards of CSOs. The comparison between the results of these two approaches highlighted the importance of simultaneously considering many scenarios for assessing the risk of contamination of source waters. It was possible to use the Bayesian network rather than the deterministic equation, which only supports one scenario at a time. It was also shown that the deterministic approach often overestimated risk levels for CSO outfalls close to the water intake. This occurred because the assessment process emphasized the distance factor between the discharge point and the water intake, while neglecting other crucial characteristics of the overflow, such as duration and frequency. In particular, the deterministic approach tended to underestimate risk for CSOs associated with low overflow frequencies as it did not support scenarios of overflow duration, unlike the probabilistic approach. The validation and sensitivity analysis of the Bayesian model revealed that the population residing in the CSO's drainage basin, along with the frequency and duration of the overflows, exerted the greatest influence on the resulting risk levels. These factors outweighed other variables utilized in the risk assessment, including vulnerability of the drinking water intake, the type of overflow recorder, pipe diameter, and variables defining the exposure of the water intake to the discharge. In the context of implementing action plans, the Bayesian network is estimated as a cost-effective technique as it prioritized overflow structures needing special attention in a highly urbanized watershed, where the same CSOs were deterministically rated as having the same risk level. The results also demonstrated the effectiveness of the Bayesian model in addressing data gaps faced by water managers and stakeholders. The Bayesian model proved capable of assessing risks with uncertainties for CSOs, even with limited input data available. These findings can assist managers in identifying problematic structures by considering various scenarios, unlike the deterministic approach, which left almost half (n = 42) of the study site's overflow structures unassessed due to data limitations.

Food consumption and tobacco smoke are the main sources of toxic trace elements (TTE) for humans. To the present, no study has been carried out that assessed human exposure to TTE (Cd, Pb, As, Ni, Cr, Cu, and Co) through the consumption of the tomatoes, rice, and tobacco crops grown in the Sancti Spiritus territory of Cuba. Accordingly, the main goal of this study was to assess which metals and crops should receive priority attention for metal pollution management in the local environment. Combining residue element analysis in crops with consumption data collected from a survey, a deterministic exposure assessment was performed. The study identified that priority attention should be focused on Ni and Cd. First, the average concentration of Ni in tomato and rice was found above their reference limits. As a consequence, the concentration of Ni represented a risk to the maximum scenario of children, adolescents, adults, and the elderly. Together with Ni, Cd, and Cu also contribute slightly to the cumulative risk. Then, Cd and Ni were quantified in tobacco smoke at a concentration that represented an equal risk to both active and passive smokers. Concentrations high enough to hazard from these toxic elements. The study helped to identify children as the highest stratum at risk of developing adverse health effects due to exposure to Ni and Cd. The results obtained from the basis for future research aimed at reducing the polluting pressure of TTE on human health and the environment. [ABSTRACT FROM AUTHOR]

Use of glyphosate in crop production can lead to residues of the active substance and related metabolites in food. Glyphosate has never been considered acutely toxic; however, in 2015 the European Food Safety Authority (EFSA) proposed an acute reference dose (ARfD). This differs from the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) who in 2016, in line with their existing position, concluded that an ARfD was not necessary for glyphosate. This paper makes a comprehensive assessment of short-term dietary exposure to glyphosate from potentially treated crops grown in the EU and imported third-country food sources. European Union and global deterministic models were used to make estimates of short-term dietary exposure (generally defined as up to 24 h). Estimates were refined using food-processing information, residues monitoring data, national dietary exposure models, and basic probabilistic approaches to estimating dietary exposure. Calculated exposures levels were compared to the ARfD, considered to be the amount of a substance that can be consumed in a single meal, or 24-h period, without appreciable health risk. Acute dietary intakes were <100% of the ARfD for all foodstuffs, except wild fungi, when calculated using the EFSA model. The model assumptions differ from those of the source model (German national model), resulting in the use of a higher variability factor. Intakes estimated with the German model represented only 18% of the ARfD. The impact of differing assumptions regarding variability and other input parameters is discussed. Probabilistic exposure estimates showed that the acute intake on no person-days exceeded 10% of the ARfD, even for the pessimistic scenario. [ABSTRACT FROM AUTHOR]

Deterministic risk assessments provide a single point estimate of risk at a site of concern, while probabilistic risk assessment methods generate a range of values from probability distribution functions (PDFs). This study compares deterministic and probabilistic risk assessment methods for two different sites using uncertainty analysis and evaluates the use of toxic equivalency factors (TEFs) for polycyclic aromatic hydrocarbons (PAHs) in each method. The use of TEFs allowed more of the PAHs to be included which resulted in higher risk estimates for both adults and children at both study sites. Exposure factor variability generated greater uncertainty in risk estimates than sample heterogeneity or toxicity estimates. TEFs allowed for a more complete representation of the toxicity contributions from PAH species present at the study sites. Exposure factor distributions together with TEF estimations for toxicity of PAH species provide an assessment that can reduce and account for uncertainty. Probabilistic risk estimates provide a sensible improvement to deterministic risk estimates by generating a range of risk values, along with an average estimate and the degree of conservatism of those estimates. [ABSTRACT FROM AUTHOR]

There is an ongoing discussion whether in the environmental risk assessment for chemicals the so called ‘deterministic’ approach using point estimates of exposure and effect concentrations is still appropriate. Instead, the more detailed and scientifically sounder probabilistic methods that have been developed over the last years are widely recommended. Here, we present the results of a probabilistic effect assessment for the aquatic environment performed for the pesticide methyl parathion and compare them with the results obtained with the common deterministic approach as described in the EU Technical Guidance Document. Methyl parathion was chosen because a sufficient data set (acute toxicity data for about 70 species) was available. The assumptions underlying the probabilistic effect assessment are discussed in the light of the results obtained for methyl parathion. Two important assumptions made by many studies are: (i) a sufficient number of ecologically relevant toxicity data is available, (ii) the toxicity data follow a certain distribution such as log-normal. Considering the scarcity of data for many industrial chemicals, we conclude that these assumptions would not be fulfilled in many cases if the probabilistic assessment was applied to the majority of industrial chemicals. Therefore, despite the well-known limitations of the deterministic approach, it should not be replaced by probabilistic methods unless the assumptions of these methods are carefully checked in each individual case, which would significantly increase the effort for the assessment procedure. [ABSTRACT FROM AUTHOR]