Environmental Risk Assessment Methodology Research Articles

Continuous-flow laboratory simulation of stream water quality changes downstream of an untreated wastewater discharge

In regions of the world with poor provision of wastewater treatment, raw sewage is often discharged directly into surface waters. This paper describes an experimental evaluation of the fate of two organic chemicals under these conditions using an artificial channel cascade fed with a mix of settled sewage and river water at its upstream end and operated under continuous steady-state conditions. The experiments underpin an environmental risk assessment methodology based on the idea of an “impact zone” (IZ) – the zone downstream of wastewater emission in which water quality is severely impaired by high concentrations of unionised ammonia, nitrite and biochemical oxygen demand (BOD). Radiolabelled dodecane-6-benzene sulphonate (DOBS) and aniline hydrochloride were used as the model chemical and reference compound respectively. Rapid changes in 14C counts were observed with flow-time for both these materials. These changes were most likely to be due to complete mineralisation. A dissipation half-life of approximately 7.1 h was observed for the 14C label with DOBS. The end of the IZ was defined as the point at which the concentration of both unionised ammonia and nitrite fell below their respective predicted no-effect concentrations for salmonids. At these points in the cascade, approximately 83 and 90% of the initial concentration of 14C had been removed from the water column, respectively. A simple model of mineral nitrogen transformations based on Michaelis–Menten kinetics was fitted to observed concentrations of NH 4, NO 2 and NO 3. The cascade is intended to provide a confirmatory methodology for assessing the ecological risks of chemicals under direct discharge conditions.

Characterisation of background dose-rates for marine environments

Environmental risk assessment methodologies often require background dose-rates for wild flora and fauna to be derived in a robust and transparent way. To facilitate this task, information can be organised around reference organisms (ROs), entities that can be used as representatives of the broader ecosystem. In this study, generic datasets have been collated on levels of naturally occurring radionuclides in sediments, seawater and ROs for marine ecosystems. In some cases, data gap filling methods have been required owing to a paucity of information. Once full datasets have been acquired, dose conversion coefficients (DCCs) can be applied and dose-rate calculations can be performed probabilistically allowing the variability in the underlying datasets to be accounted for. Unweighted absorbed dose-rates for marine reference organisms lie between 0.02–1.2 µGy h-1 , whereas weighted dose-rates fall in the range 0.08 µGy h-1 to 8.8 µGy h-1 . Except for the special case of sea anemones/corals, the most important nuclides for the total dose-rates are 210 Po and 226 Ra for heterotrophic ROs (i.e. all vertebrate and invertebrate animals), whereas 226 Ra and 228 Th contribute most for autotrophic ROs (i.e. macroalgae, phytoplankton and aquatic plants). In addition, 40 K has a considerable impact on unweighted dose-rates for all ROs. Non-parametric statistical tests have been applied to show whether there are differences between activity concentrations data for ROs and ICRP-defined Reference Animals and Plants (RAPs).

Environmental Risk Management of an Abandoned Mining Site in Hungary

An Environmental Risk Management methodology was developed for the Toka catchment area, an abandoned base metal mining site in Gyöngyösoroszi, Hungary. The postmining activities on the Hungarian site require the management of both the point and diffuse sources. The mobile Cd and Zn content of the mine waste, soil and sediment transported by water pose the highest environmental risk in the area. The approach is „GIS based” (Geographical Information System) and „catchment scale”, using a three tiered, iterative Environmental Risk Assessment methodology. The model parameters of the metal transport were determined in leaching microcosms. The risk reduction concept aims at reducing the runoff water quantity and contamination by removal of the point sources and chemical & phytostabilisation of the residual and diffuse pollution. The planning of the field application was based on the results of the stabilisation microcosms.

Environmental Toxicity Testing in the Risk Assessment of a Metal Contaminated Abandoned Mining Site in Hungary

A three tiered, iterative Environmental Risk Assessment methodology, including preliminary Qualitative Risk Assessment, Quantitative Hazard Assessment and Site Specific Quantitative Risk Assessment, was established to assess the environmental risk of point and diffuse pollution of mining origin at catchment scale [1]. The model site was an abandoned Pb and Zn sulphide ore mine in Gyöngyösoroszi, Toka-valley, NE Hungary [2]. The Integrated Risk Model considers the sources identified by the GIS-based (Geographical Information System) pollution map, the transport routes shown by the GIS-based flow accumulation model and the receptors of different land uses in the catchment. The site-specific quantitative risk was characterised by the Soil Testing Triad [3]. The three elements of the Triad are: physico-chemical analyses of the soil and the contaminants, the biological characterisation and ecotoxicity testing of the contaminated soil, measuring the response of single species in laboratory bioassays, the natural response of the soil microflora and plants or the dynamic response of the whole soil in microcosms. The Triad approach strongly supports the characterisation of the site specific risk as well as the selection and planning of the suitable remediation option.

Comparing Occupational and Environmental Risk Assessment Methodologies Using Pharmacokinetic Modeling

Human health risks from occupational exposures are managed by limiting exposures to acceptable levels established by the American Conference of Governmental Industrial Hygienists or another similar body. Acceptable environmental exposures are benchmarked by values such as U.S. Environmental Protection Agency's Reference Doses and Reference Concentrations. The approaches to establishing these values are different, as are the groups they are intended to protect, complicating direct comparisons. Occupational limits are based on a healthy workforce in a narrow age range and do not generally consider sensitive populations. Limits for environmental exposures consider sensitive populations. In this evaluation, physiologically based pharmacokinetic modeling was used to predict tissue doses from acceptable/safe exposures as established by different organizations and agencies. Internal doses calculated for an agency's acceptable/safe exposures via oral and inhalation routes may differ substantially, but are sometimes in excellent agreement. The finding that internal doses resulting from occupational exposures are almost uniformly greater than those from environmental exposures suggests different mindsets among these groups regarding how safe is “safe.”

The use of environmental risk assessment methodologies for an indoor air quality investigation

The authors of this paper chose several target compounds that have been found in average US homes, applied the current United States Environmental Protection Agency (USEPA) Superfund risk assessment methodologies to indoor air quality, and produced risk numbers for hazard quotients and predicted increases in incidence of cancer which would be unacceptable at US hazardous waste sites. The calculations were made for the average child and adult with USEPA default exposure values. Calculations were also made for a worst case scenario using maximum concentrations and exposure estimates defined by the USEPA as describing the reasonable exposure (RME). Significant cancer risks and non-cancer hazard quotients were predicted.

Methodology for Environmental Risk Assessment of Industrial Nonroutine Releases

While increasing social concern and strict legislation have resulted in expanding the conventional design objectives of profitability to include environmental impact and operability aspects, traditional practices regarding environmental risk assessment (ERA) have mainly focused on providing qualitative guidelines to evaluate the likelihood and consequence of undesired events to the environment. By linking process reliability considerations to environmental impact analysis within a process optimization framework, this work presents a systematic method for the quantification and at source minimization of combined adverse environmental effects of routine (i.e., waste water effluent streams) and nonroutine releases (i.e., leaks, emissions from equipment breakdown). Trade-offs are explored regarding cost and routine/nonroutine environmental impact objectives, while opportunities for effective maintenance strategies are identified. The steps of the theoretical analysis and the potential of the proposed methodology are illustrated with two example problems, a simplified chemical reaction-separation scheme and a methane chlorination process.