Risk Assessment of Per- and Polyfluoroalkyl Substance Mixtures: A Relative Potency Factor Approach.

Per- and polyfluoroalkyl substances (PFAS) often occur together as contamination in exposure media such as drinking water or food. The relative potency factor (RPF) methodology facilitates the risk assessment of mixture exposure. A database of liver endpoints was established for 16 PFAS, using data with the same species (rat), sex (male), and exposure route (oral) and comparable exposure duration (42-90 d). Dose-response analysis was applied to derive the relative potencies of 3 perfluoroalkyl sulfonic acids (perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid), 8 perfluoroalkyl carboxylic acids (perfluorobutanoic acid, perfluorohexanoic acid, perfluorononanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotetradecanoic acid, perfluorohexadecanoic acid, perfluorooctadecanoic acid), 2 perfluoroalkyl ether carboxylic acids (tetrafluoro-2-[heptafluoropropoxy]propanoic acid, 3H-perfluoro-3-[(3-methoxy-propoxy)propanoic acid]), and 2 fluorotelomer alcohols (6:2 FTOH, 8:2 FTOH) compared to perfluorooctanoic acid (PFOA), based on liver effects. In addition, the RPFs of 7 other perfluoroalkyl acids were estimated based on read-across. This resulted in the relative potencies of 22 PFAS compared to the potency of index compound PFOA. The obtained RPFs can be applied to measured PFAS quantities, resulting in the sum of PFOA equivalents in a mixture. This sum can be compared with an established PFOA concentration limit (e.g., in drinking water or food) or an external health-based guidance value (e.g., tolerable daily intake, acceptable daily intake, or reference dose) to estimate the risk resulting from direct oral exposure to mixtures. Assessing mixture exposure is particularly relevant for PFAS, with omnipresent exposure in our daily lives. Environ Toxicol Chem 2021;40:859-870. © 2020 SETAC.

Risk management of hazardous substances in a circular economy.

The ambitions for a circular economy are high and unambiguous, but day-to-day experience shows that the transition still has many difficulties to overcome. One of the current hurdles is the presence of hazardous substances in waste streams that enter or re-enter into the environment or the technosphere. The key question is: do we have the appropriate risk management tools to control any risks that might arise from the re-using and recycling of materials? We present some recent cases that illustrate current practice and complexity in the risk management of newly-formed circular economy chains. We also highlight how separate legal frameworks are still disconnected from each other in these cases, and how circular economy initiatives interlink with the European REACH regulation. Furthermore, we introduce a novel scheme describing how to decide whether a(n)(additional) risk assessment is necessary with regard to the re-use of materials containing hazardous substances. Finally, we present our initial views on new concepts for the fundamental integration of sustainability and safety aspects. These concepts should be the building blocks for the near future shifts in both policy frameworks and voluntary initiatives that support a sound circular economy transition.

Towards sustainable management of groundwater: policy developments in The Netherlands.

This article presents and discusses the main elements for a fundamental policy change for groundwater management in The Netherlands. The study analyzes the status and current use of groundwater, the increasing pressure in The Netherlands and many other countries on the natural soil-water system, the effects on quality and quantity of groundwater and the use of the subsoil. An overview is given of the current national and European regulations regarding groundwater and related policies for e.g. drinking water, soil policies and other interventions in the subsurface. The Dutch National Government is developing a new framework for groundwater management that aims a sustainable use of groundwater not only in environmental, but also in economic and social perspective. This framework for groundwater will benefit the Structure vision on the subsoil. The question is how 'sustainable use' can be a guiding principle in groundwater management, strengthening the relation between groundwater quantity and quality. It is proposed to define a generic National approach for the assessment of new and existing activities with potential effects on groundwater and for groundwater quality assessment. Additionally it is proposed to give local authorities the opportunity to set area-specific objectives on a regional or local scale to adjust for specific societal needs and area-specific characteristics. For setting these objectives it is recommended to use the concept of ecosystem services as a leading principle for defining the groundwater quality and quantity (e.g. for use as source for drinking water, aquifer thermal storage and sustaining terrestrial and aquatic ecosystems).

Lung cancer risk and past exposure to emissions from a large steel plant.

We studied the spatial distribution of cancer incidence rates around a large steel plant and its association with historical exposure. The study population was close to 600,000. The incidence data was collected for 1995-2006. From historical emission data the air pollution concentrations for polycyclic aromatic hydrocarbons (PAH) and metals were modelled. Data were analyzed using Bayesian hierarchical Poisson regression models. The standardized incidence ratio (SIR) for lung cancer was up to 40% higher than average in postcodes located in two municipalities adjacent to the industrial area. Increased incidence rates could partly be explained by differences in socioeconomic status (SES). In the highest exposure category (approximately 45,000 inhabitants) a statistically significant increased relative risk (RR) of 1.21 (1.01-1.43) was found after adjustment for SES. The elevated RRs were similar for men and women. Additional analyses in a subsample of the population with personal smoking data from a recent survey suggested that the observed association between lung cancer and plant emission, after adjustment for SES, could still be caused by residual confounding. Therefore, we cannot indisputably conclude that past emissions from the steel plant have contributed to the increased risk of lung cancer.

Possibilities of implementation of bioavailability methods for organic contaminants in the Dutch Soil Quality Assessment Framework.

In the Netherlands, risk assessment of contaminated soils is based on determining the total contaminant concentration. If this measured soil concentration exceeds the Soil Quality Standards (SQS) a higher tier risk evaluation must be performed. Experiences from the field have given rise to the perception that performing risk evaluations based on (measured) total concentrations may lead to an inaccurate assessment of the actual risks. Assuming that only the bioavailable fraction is capable of exerting adverse effects in the soil ecosystem, it is suggested, that by taking bioavailability into account in a (higher tier) risk evaluation, a more effect-based risk assessment can be performed. Bioavailability has been a subject of research for several decades. However up to now bioavailability has not been implemented in the Dutch Soil Quality Assessment Framework. First actions were taken in the Netherlands to determine whether the concept of bioavailability could be implemented in the risk assessment of contaminated soils and to find out how bioavailability can become part of the Dutch Soil Quality Assessment Framework. These actions have led to a concrete proposal for implementation of bioavailability methods in the risk assessment of organic contaminants in soils. This paper focuses on the chemical prediction of bioavailability for ecological risk assessment of contaminated soils.

Implementation of bioavailability in standard setting and risk assessment: suggestions based on a workshop with emphasis on metals.

Bioavailability is increasingly recognised as the key issue linking increased levels of toxicants with actually occurring adverse effects in ecosystems, whilst taking the modifying effects of the abiotic components of the environment into account. Various factors may affect bioavailability in the field, and often these factors are time- and space-dependent. This is one of the main reasons why legislators have been reluctant in implementing bioavailability in risk assessment procedures. Over the last few years, however, considerable scientific progress has been made with regard to better understanding of chemical and ecological mechanisms responsible for rendering chemicals available for uptake and toxicity. As a consequence, legislators face the challenge to anticipate the scientific progress and to implement bioavailability in legislation. This paper discusses the possibilities of implementing various methodologies within a maximum period of time of three years.

Implementation of bioavailability in standard setting and risk assessment.

Bioavailability is, to an increasing extent, recognised as the key issue linking the increased levels of toxicants to actually occurring adverse effects in ecosystems, whilst taking the modifying effects of the abiotic components of the environment into account. Various factors may affect bioavailability in the field, and these factors are often time and space dependent. This is one of the main reasons why legislators have been reluctant to implement bioavailability in risk assessment procedures. Over the last few years, however, considerable scientific progress has been made with regard to increasing our understanding of the chemical and ecological mechanisms responsible for rendering chemicals available for uptake and toxicity. As a consequence, legislators face the challenge of having to anticipate the scientific progress and to implement bioavailability in legislation. This contribution reports on the possibilities of implementing various methodologies within a maximum time period of three years.