Exposure Modelling Day 1. Adam Peters and Graham Merrington 2017
Exposure Conceptual model Wastewater Discharges Emission Scenarios 2017
Exposure Modelling ECHA Guidance for Risk Assessment R16 Based on the approaches previously used for the risk assessment of chemicals in Europe (EU TGD) Complete approach for exposure assessment defined in R16 EUSES implements the same procedures Requires minimal input information Molecular weight, vapour pressure, water solubility, log KOW Avoids making simple mistakes Spreadsheet versions can be developed 2017
Emissions Data Typically for prospective risk assessment How much of this substance will be released into the environment from this process, operation, or application? Quantities in use? Containment and potential for dispersal? Specific equipment, use at specified sites only, indoor or outdoor use, professional use only, wide spread dispersive use Routes of emission Air, water, soil (usually only indirectly via deposition from air and spreading of sewage sludges) 2017
Sewage and Wastewater Treatment Typical for large industrial sites Treatment may be on-site, off-site (municipal), or both Concentrations of chemicals in many wastewaters may not be limited by water solubility Fate during treatment Degradation, volatilisation, partitioning to sludge, and aqueous phase emitted as effluent 2017
Discharges to surface waters Discharge of sewage effluent into receiving water Takes account of dilution and partitioning to SPM May also need to consider duration and frequency of emission Peak concentrations or annual averages? 2016
Emission Scenarios Continuous emission from an industrial site Review of consented discharge Intermittent emission from an industrial site Batch processes or development work Accidental emission directly into the environment Spillages, fires, shipwreck Land application of materials exempt from waste management licencing Residual medicines in manures 2017
Emission Source Mass of substance used Frequency of use, emission days Fraction emitted Treatment efficiency Effluent flow rate 2017
Spatial Scales Local Regional Continental e.g. the area surrounding an industrial site, farm, or waste management facility Regional Usually taken to be a whole country, but could be smaller, e.g. a county Likely to include a number of similar operations Continental Aggregation of several regions 2017
Background Concentrations May arise from widespread use and emission of substances Legacy substances still found in the environment Also relevant to naturally occurring substances Sometimes considered for compliance assessment of metals Only likely to be relevant for marginal failures 2017
Sewage Treatment Removal of BOD & suspended solids Also degradation of some organic chemicals Other removal processes Adsorption to sludge –partitioning substances Volatilisation – volatile substances Degree of degradation and removal can be highly variable between different works Limited useful information SIMPLETreat estimates 2017
Soil Exposures Atmospheric deposition of air emissions Land spreading of sewage sludges Land spreading of other waste materials Particular Issues Averaging period for exposure duration Relevant soil depth Accumulation models 2017
Emission to Environment Wastewater discharge into a river Concentration of substance in discharge Size (flow rate) of discharge relative to river? Partitioning of substance in river Deposition to sediments Resulting dissolved concentration in river after dilution Are local sediments likely to become contaminated? Are there any potential concerns for local predators? Are there any potential concerns for local fishermen? 2017
2016