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Category: Environmental Microbiology
Exposure Assessment, Page 1 of 2
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Exposure assessment is the evaluation of the magnitude and frequency of exposure to pathogenic organisms via specified exposure pathways. Exposure assessment consists of three steps including: defining the exposure pathway; quantifying each model variable; and finally quantitatively characterizing the magnitude and frequency of exposure. In this chapter, these three steps are described in detail including considerations for data interpretation and statistical inference. Numerical examples related to drinking water consumption, wastewater irrigation of food crops and recreational water quality are provided.
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Conceptual components for quantifying exposure. doi:10.1128/9781555818821.ch3.5.2.f1
Conceptual components for quantifying exposure. doi:10.1128/9781555818821.ch3.5.2.f1
Schematic of exposure pathway applied for the assessment of norovirus risk via drinking water in Japan. doi:10.1128/9781555818821.ch3.5.2.f2
Schematic of exposure pathway applied for the assessment of norovirus risk via drinking water in Japan. doi:10.1128/9781555818821.ch3.5.2.f2
Quantified model inputs and exposure calculated for the assessment of norovirus risk via drinking water in Japan. doi:10.1128/9781555818821.ch3.5.2.f3
Quantified model inputs and exposure calculated for the assessment of norovirus risk via drinking water in Japan. doi:10.1128/9781555818821.ch3.5.2.f3
Native versus spiked oocyst counts from a surface water source in Australia. doi:10.1128/9781555818821.ch3.5.2.f4
Native versus spiked oocyst counts from a surface water source in Australia. doi:10.1128/9781555818821.ch3.5.2.f4
Maximum likelihood (solid line) and 95th percentile credible interval (dashed lines) for the gamma-distributed Cryptosporidium oocyst concentration in the surface water source (a) without considering recovery, and (b) correcting each Cryptosporidium count using an internal ColorSeed recovery control. doi:10.1128/9781555818821.ch3.5.2.f5
Maximum likelihood (solid line) and 95th percentile credible interval (dashed lines) for the gamma-distributed Cryptosporidium oocyst concentration in the surface water source (a) without considering recovery, and (b) correcting each Cryptosporidium count using an internal ColorSeed recovery control. doi:10.1128/9781555818821.ch3.5.2.f5
Examples of fitted beta-distributions (inserts) and predicted source water Cryptosporidium oocyst concentration PDFs, including credible intervals, for various recovery data set sizes. Reprinted from ref 22, with permission. doi:10.1128/9781555818821.ch3.5.2.f6
Examples of fitted beta-distributions (inserts) and predicted source water Cryptosporidium oocyst concentration PDFs, including credible intervals, for various recovery data set sizes. Reprinted from ref 22, with permission. doi:10.1128/9781555818821.ch3.5.2.f6
Schematic of exposure pathway applied for the assessment of enteric virus risk via consumption of wastewater irrigated lettuce crops. doi:10.1128/9781555818821.ch3.5.2.f7
Schematic of exposure pathway applied for the assessment of enteric virus risk via consumption of wastewater irrigated lettuce crops. doi:10.1128/9781555818821.ch3.5.2.f7
Schematic of exposure pathway applied for comparing the exposure to pathogens depending on the fecal source to recreational waters. doi:10.1128/9781555818821.ch3.5.2.f8
Schematic of exposure pathway applied for comparing the exposure to pathogens depending on the fecal source to recreational waters. doi:10.1128/9781555818821.ch3.5.2.f8
Predicted GI illness by reference pathogen (median, interquartile range, 10th and 90th percentiles, minimum, and maximum) for adults following a single accidental ingestion of recreational water containing fresh fecal contamination at 35 cfu/100 /ml enterococci contributed by seagulls or primary POTW effluent (T) total GI risk, (C.j.) C. jejuni risk; (S) Salmonella risk; (C) Cryptosporidium risk; (G) Giardia risk; (N) Norovirus risk). Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f9
Predicted GI illness by reference pathogen (median, interquartile range, 10th and 90th percentiles, minimum, and maximum) for adults following a single accidental ingestion of recreational water containing fresh fecal contamination at 35 cfu/100 /ml enterococci contributed by seagulls or primary POTW effluent (T) total GI risk, (C.j.) C. jejuni risk; (S) Salmonella risk; (C) Cryptosporidium risk; (G) Giardia risk; (N) Norovirus risk). Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f9
Spearman rank correlation coefficient for exposure parameter inputs to the predicted probability of GI illness from accidental ingestion of recreation water containing fresh fecal contamination at 35 cfu/100 ml ENT for (a) seagull feces and (b) primary POTW effluent. Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f10
Spearman rank correlation coefficient for exposure parameter inputs to the predicted probability of GI illness from accidental ingestion of recreation water containing fresh fecal contamination at 35 cfu/100 ml ENT for (a) seagull feces and (b) primary POTW effluent. Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f10
Parametric sensitivity analysis of the predicted probability of gastrointestinal illness (median, 10th, and 90th percentiles) for adults attributable to Campylobacter jejuni from accidental ingestion of recreational water containing fresh seagull fecal contamination at 35 cfu/100 ml ENT to changes in the assumed fraction of total C. jejuni strains from seagulls that are human infectious. Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f11
Parametric sensitivity analysis of the predicted probability of gastrointestinal illness (median, 10th, and 90th percentiles) for adults attributable to Campylobacter jejuni from accidental ingestion of recreational water containing fresh seagull fecal contamination at 35 cfu/100 ml ENT to changes in the assumed fraction of total C. jejuni strains from seagulls that are human infectious. Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f11
Comparison of median illness risk for adults when total ENT concentration (at 35 cfu/100 ml) is attributed to a mixture of primary POTW effluent (sewage) and seagull feces (gulls). Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f12
Comparison of median illness risk for adults when total ENT concentration (at 35 cfu/100 ml) is attributed to a mixture of primary POTW effluent (sewage) and seagull feces (gulls). Reprinted from ref 58, with permission. doi:10.1128/9781555818821.ch3.5.2.f12
Examples of different exposure pathways (sources and barriers) for the same exposure scenario (adapted from (1)).
Examples of different exposure pathways (sources and barriers) for the same exposure scenario (adapted from (1)).
Statistics for describing model variables for exposure assessment
Statistics for describing model variables for exposure assessment
Examples of exposure magnitude and frequency assumptions for microbial risk assessment: combination of scientific data and reference values (from Australian Guidelines for Water Recycling: Table 3.3 Intended uses and associated exposure for recycled water [ 43 ])
Examples of exposure magnitude and frequency assumptions for microbial risk assessment: combination of scientific data and reference values (from Australian Guidelines for Water Recycling: Table 3.3 Intended uses and associated exposure for recycled water [ 43 ])
Best and extreme estimates of model parameters applied in the exposure assessment of virus exposure via wastewater irrigated lettuce crops
Best and extreme estimates of model parameters applied in the exposure assessment of virus exposure via wastewater irrigated lettuce crops
Step characteristic and factor sensitivity calculated for the lettuce crop exposure model
Step characteristic and factor sensitivity calculated for the lettuce crop exposure model