Human biomonitoring and toxicokinetics as key building blocks for next generation risk assessment.

Human health risk assessment is historically built upon animal testing, often following Organisation for Economic Co-operation and Development (OECD) test guidelines and exposure assessments. Using combinations of human relevant in vitro models, chemical analysis and computational (in silico) approaches bring advantages compared to animal studies. These include a greater focus on the human species and on molecular mechanisms and kinetics, identification of Adverse Outcome Pathways and downstream Key Events as well as the possibility of addressing susceptible populations and additional endpoints. Much of the advancement and progress made in the Next Generation Risk Assessment (NGRA) have been primarily focused on new approach methodologies (NAMs) and physiologically based kinetic (PBK) modelling without incorporating human biomonitoring (HBM). The integration of toxicokinetics (TK) and PBK modelling is an essential component of NGRA. PBK models are essential for describing in quantitative terms the TK processes with a focus on the effective dose at the expected target site. Furthermore, the need for PBK models is amplified by the increasing scientific and regulatory interest in aggregate and cumulative exposure as well as interactions of chemicals in mixtures. Since incorporating HBM data strengthens approaches and reduces uncertainties in risk assessment, here we elaborate on the integrated use of TK, PBK modelling and HBM in chemical risk assessment highlighting opportunities as well as challenges and limitations. Examples are provided where HBM and TK/PBK modelling can be used in both exposure assessment and hazard characterization shifting from external exposure and animal dose/response assays to animal-free, internal exposure-based NGRA.

A Human Biomonitoring Study Assessing Glyphosate and Aminomethylphosphonic Acid (AMPA) Exposures among Farm and Non-Farm Families.

Glyphosate-based pesticides are the highest-volume used herbicides worldwide. International concerns regarding the potential human adverse effects of glyphosate exposures have heightened since IARC classified glyphosate as probably carcinogenic to humans. Human biomonitoring (HBM) studies have identified ubiquitous exposure to glyphosate and its main breakdown product, aminomethylphosphonic acid (AMPA), from environmental exposures. The IMAGE research project aimed to investigate farm and non-farm families' exposure to glyphosate while aligning with the Human Biomonitoring for Europe (HBM4EU) initiative. The study recruited non-farm and farm families (who use glyphosate on their farms). Each family member provided a urine sample that was analysed using gas chromatography coupled with tandem mass spectrometry, with a limit of quantification of 0.05 µg/L for glyphosate and AMPA. In addition to general information on background exposures in farm and non-farm families, we investigated relationships in exposure between families and family members. We recruited 68 families, including 54 non-farm and 14 farm families (180 vs. 45 individuals). Some pesticide users (n = 14, all male farmers) had slightly elevated AMPA levels compared to other adult participants but, overall, we observed no significant differences between farm and non-farm families. The main metabolite, AMPA, was quantifiable in twice as many samples as glyphosate (61% vs. 32%), with a maximum concentration of 7.24 µg/L vs. 3.21 µg/L. Compared to previous studies, exposure levels were relatively low and far below current health-based guidance values (3% or less for glyphosate and AMPA). Study results suggest potential exposures from residential co-exposures or living with a pesticide user. This is the first study internationally to investigate glyphosate and AMPA across family members (farm and non-farm). We found comparably low glyphosate and AMPA exposures among these families. These results enhance our understanding of glyphosate exposures for different demographic groups and contribute to the scientific knowledge on exposures required for regulatory risk assessments and the re-evaluation of glyphosate in 2022 by the European Commission.

The European exposure science strategy 2020-2030.

Exposure science is an emerging and rapidly growing field dedicated to all aspects concerning the contact between chemical, biological, physical or psycho-social stressors and human and ecological receptors. With that, exposure science plays a central role in protecting human and ecosystem health, and contributes to the global transition towards a green and sustainable society. In Europe, however, exposure science is currently not sufficiently recognised as a scientific field, resulting in inefficient uptake into policies. In response, the wider European exposure science community developed elements and actions under the auspices of the Europe Regional Chapter of the International Society of Exposure Science (ISES Europe), for identified priority areas, namely education, exposure models, exposure data, human biomonitoring, and policy uptake. In the present document, we synthesize these strategic elements into an overarching 'European Exposure Science Strategy 2020-2030', following three strategic objectives that focus on acknowledging exposure science as an independent and interconnected field, harmonizing approaches and tools across regulations, and exploring collaboration, education and funding mechanisms. To operationalise this strategy, we present concrete key actions and propose initiatives and funding options for advancing the underlying science, cultivating broader education and cross-sector exposure knowledge transfer, and fostering effective uptake of exposure information into policy. We aim at anchoring European efforts in the global exposure science context, with a special focus on the interface between scientific advancements, application in decision support, and dissemination and training. This will help to develop exposure science as a strong scientific field with the ultimate goal to successfully assess and manage various stressors across sectors and geographic scales.

Developing human biomonitoring as a 21st century toolbox within the European exposure science strategy 2020-2030.

Human biomonitoring (HBM) is a crucial approach for exposure assessment, as emphasised in the European Commission's Chemicals Strategy for Sustainability (CSS). HBM can help to improve chemical policies in five major key areas: (1) assessing internal and aggregate exposure in different target populations; 2) assessing exposure to chemicals across life stages; (3) assessing combined exposure to multiple chemicals (mixtures); (4) bridging regulatory silos on aggregate exposure; and (5) enhancing the effectiveness of risk management measures. In this strategy paper we propose a vision and a strategy for the use of HBM in chemical regulations and public health policy in Europe and beyond. We outline six strategic objectives and a roadmap to further strengthen HBM approaches and increase their implementation in the regulatory risk assessment of chemicals to enhance our understanding of exposure and health impacts, enabling timely and targeted policy interventions and risk management. These strategic objectives are: 1) further development of sampling strategies and sample preparation; 2) further development of chemical-analytical HBM methods; 3) improving harmonisation throughout the HBM research life cycle; 4) further development of quality control / quality assurance throughout the HBM research life cycle; 5) obtain sustained funding and reinforcement by legislation; and 6) extend target-specific communication with scientists, policymakers, citizens and other stakeholders. HBM approaches are essential in risk assessment to address scientific, regulatory and societal challenges. HBM requires full and strong support from the scientific and regulatory domain to reach its full potential in public and occupational health assessment and in regulatory decision-making.

Framework for developing an exposure science curriculum as part of the European Exposure Science Strategy 2020-2030.

BACKGROUND: Evaluating and managing exposures to chemical, physical and biological stressors, which frequently interplay with psychological stressors as well as social and behavioural aspects, is crucial for protecting human and environmental health and transitioning towards a sustainable future. Advances in our understanding of exposure rely on input from well-trained exposure scientists. However, no education programmes in Europe are currently explicitly dedicated to cover the broader range of exposure science approaches, applications, stressors and receptors. OBJECTIVE: To address this challenge, a curriculum is needed that yields credible, well-defined career pathways in exposure science. METHODS: Needs and conditions for advancing exposure science education in Europe were identified. As a starting point for a way forward, harmonised learning outcomes for exposure science were defined at each level of the European Qualifications Framework. The course programme coordinators were recruited for three varying courses, with respect to the course level and the proportion of the curriculum dedicated to exposure science. These courses were assessed via our systematic course review procedure. Finally, strategic objectives and actions are proposed to build exposure science education programmes. RESULTS: The ISES Europe 'Education, Training and Communication' expert working group developed a framework for creating a viable exposure science curriculum. Harmonised learning outcomes were structured under eight learning levels, categorised by knowledge, skills and competence. Illustrative case studies demonstrated how education providers integrated these learning outcomes for their educational context and aligned the overall exposure science curriculum. CONCLUSIONS: The international recognition and adoption of exposure science education will enable advances in addressing global exposure science challenges for various stressors, from behavioural aspects from individual to population scale, and effective communication between exposure scientists and relevant stakeholders and policy makers, as part of the European Exposure Science Strategy 2020-2030.

Sensitive and selective quantification of glyphosate and aminomethylphosphonic acid (AMPA) in urine of the general population by gas chromatography-tandem mass spectrometry.

Glyphosate is the highest volume herbicide used worldwide, and its main biodegradation product is aminomethylphosphonic acid (AMPA), both are listed as priority substances in the Human Biomonitoring for Europe (HBM4EU) initiative which aims at improving policy by filling knowledge gaps by targeted research. The objective of the current study was to advance the sensitivity of an existing gas chromatography-tandem mass spectrometry analytical method to measure environmental population exposures. A 50% lower limit of quantification of 0.05 µg/L was achieved for both analytes by slight modifications in sample work-up, and use of another isotope labelled internal standard. In a pilot study, 41 urine samples from the general German population were analysed, of which glyphosate and AMPA could be quantified in 66% and 90% of the samples respectively, which is sufficient to reliably describe distributions of urinary concentrations in the non-occupationally exposed population.

Human Biomonitoring of Glyphosate Exposures: State-of-the-Art and Future Research Challenges.

Glyphosate continues to attract controversial debate following the International Agency for Research on Cancer carcinogenicity classification in 2015. Despite its ubiquitous presence in our environment, there remains a dearth of data on human exposure to both glyphosate and its main biodegradation product aminomethylphosphonic (AMPA). Herein, we reviewed and compared results from 21 studies that use human biomonitoring (HBM) to measure urinary glyphosate and AMPA. Elucidation of the level and range of exposure was complicated by differences in sampling strategy, analytical methods, and data presentation. Exposure data is required to enable a more robust regulatory risk assessment, and these studies included higher occupational exposures, environmental exposures, and vulnerable groups such as children. There was also considerable uncertainty regarding the absorption and excretion pattern of glyphosate and AMPA in humans. This information is required to back-calculate exposure doses from urinary levels and thus, compared with health-based guidance values. Back-calculations based on animal-derived excretion rates suggested that there were no health concerns in relation to glyphosate exposure (when compared with EFSA acceptable daily intake (ADI)). However, recent human metabolism data has reported as low as a 1% urinary excretion rate of glyphosate. Human exposures extrapolated from urinary glyphosate concentrations found that upper-bound levels may be much closer to the ADI than previously reported.

Building a European exposure science strategy.

Exposure information is a critical element in various regulatory and non-regulatory frameworks in Europe and elsewhere. Exposure science supports to ensure safe environments, reduce human health risks, and foster a sustainable future. However, increasing diversity in regulations and the lack of a professional identity as exposure scientists currently hamper developing the field and uptake into European policy. In response, we discuss trends, and identify three key needs for advancing and harmonizing exposure science and its application in Europe. We provide overarching building blocks and define six long-term activities to address the identified key needs, and to iteratively improve guidelines, tools, data, and education. More specifically, we propose creating European networks to maximize synergies with adjacent fields and identify funding opportunities, building common exposure assessment approaches across regulations, providing tiered education and training programmes, developing an aligned and integrated exposure assessment framework, offering best practices guidance, and launching an exposure information exchange platform. Dedicated working groups will further specify these activities in a consistent action plan. Together, these elements form the foundation for establishing goals and an action roadmap for successfully developing and implementing a 'European Exposure Science Strategy' 2020-2030, which is aligned with advances in science and technology.

Occupational Exposures in an Equestrian Centre to Respirable Dust and Respirable Crystalline Silica.

Sand-based products are regularly used as footing material on indoor equestrian arenas, creating a potential occupational exposure risk for respirable crystalline silica (RCS) for equestrian workers training and exercising horses in these environments. The objective of this study was to evaluate an equestrian worker's personal RCS and respirable dust (RD) exposure. Sixteen personal full-shift RD measurements were collected from an equestrian worker and analysed for RD, quartz and cristobalite. Geometric mean exposures of 0.12 mg m-3 and 0.02 mg m-3 were calculated for RD and RCS concentrations, respectively. RCS exposures of between 0.01 to 0.09 mg m-3 were measured on days when the indoor arena surface was not watered, compared to lower exposures (

Evaluating Glyphosate Exposure Routes and Their Contribution to Total Body Burden: A Study Among Amenity Horticulturalists.

OBJECTIVE: To evaluate determinants of dermal and inadvertent ingestion exposure and assess their contribution to total body burden among amenity horticultural users using glyphosate-based pesticide products. METHODS: A dermal and inadvertent ingestion exposure assessment was completed alongside a biomonitoring study among amenity horticultural workers. Linear mixed effect regression models were elaborated to evaluate determinants of exposure and their contribution to total body burden. RESULTS: A total of 343 wipe and glove samples were collected from 20 workers across 29 work tasks. Geometric mean (GM) glyphosate concentrations of 0.01, 0.04 and 0.05 µg cm-2 were obtained on wipes from the workers' perioral region and left and right hands, respectively. For disposable and reusable gloves, respectively, GM glyphosate concentrations of 0.43 and 7.99 µg cm-2 were detected. The combined hand and perioral region glyphosate concentrations explained 40% of the variance in the urinary (µg l-1) biomonitoring data. CONCLUSION: To the author's knowledge, this is the first study to have investigated both dermal and inadvertent exposure to glyphosate and their contribution to total body burden. Data show the dermal exposure is the prominent route of exposure in comparison to inadvertent ingestion but inadvertent ingestion may contribute to overall body burden. The study also identified potential exposure to non-pesticide users in the workplace and para-occupational exposures.

Exploring the half-life of glyphosate in human urine samples.

BACKGROUND: The International Agency for Research on Cancer (IARC) has recently classified glyphosate as a Group 2A 'probably carcinogenic to humans'. Due to this carcinogenic classification and resulting international debate, there is an increased demand for studies evaluating human health effects from glyphosate exposures. There is currently limited information on human exposures to glyphosate and a paucity of data regarding glyphosate's biological half-life in humans. OBJECTIVE: This study aims to estimate the human half-life of glyphosate from human urine samples collected from amenity horticulture workers using glyphosate based pesticide products. METHODS: Full void urine spot samples were collected over a period of approximately 24 h for eight work tasks involving seven workers. The elimination time and estimation of the half-life of glyphosate using three different measurement metrics: the unadjusted glyphosate concentrations, creatinine corrected concentrations and by using Urinary Excretion Rates (UER) (µg L-1, µmol/mol creatinine and UER µg L-1) was calculated by summary and linear interpolation using regression analysis. RESULTS: This study estimates the human biological half-life of glyphosate as approximately 5 ½, 10 and 7 » hours for unadjusted samples, creatinine corrected concentrations and by using UER (µg L-1, µmol/mol creatinine, UER µg L-1), respectively. The approximated glyphosate half-life calculations seem to have less variability when using the UER compared to the other measuring metrics. CONCLUSION: This study provides new information on the elimination rate of glyphosate and an approximate biological half-life range for humans. This information can help optimise the design of sampling strategies, as well as assisting in the interpretation of results for human biomonitoring studies involving this active ingredient. The data could also contribute to the development or refinement of Physiologically Based PharmacoKinetic (PBPK) models for glyphosate.

Characterising glyphosate exposures among amenity horticulturists using multiple spot urine samples.

BACKGROUND: Glyphosate has recently received much public attention following its 'Group 2A - probably carcinogenic to humans' classification from the International Agency for Research on Cancer. Despite the widespread use of glyphosate, there is limited data on potential exposures during common occupational uses. OBJECTIVE: The study aimed to characterise occupational exposures to glyphosate among amenity horticulturists through the collection and analysis of urine samples following pesticide application. The impact of work practices on personal exposure, as well as suitability of collecting multiple spot urine samples as a sampling strategy for the assessment of occupational exposure for glyphosate were also examined. METHODS: A minimum of three spot urine samples were collected per work task; before the work task began, after the work task completion and the following first morning void. All samples were analysed separately for glyphosate using liquid chromatography tandem mass spectrometry and for creatinine. Differences in urinary glyphosate concentrations between the pre-task samples versus the post-task and the peak urinary samples were both analysed using paired Student t-tests. Determinants of exposure on glyphosate urine concentrations were evaluated using Pearson's correlation coefficients and linear regression. A multivariate mixed effect model were elaborated to compare the glyphosate concentrations between post-task and following first morning void samples. In these models, worker identity was entered as a random effect to account for the presence of correlations between repeated measurements from the same individuals. RESULTS: Peak urine glyphosate concentrations measured for work tasks were 2.5, 1.9, 1.9 and 7.4 µg L-1 (arithmetic mean, geometric mean, median and maximum value, respectively). Concentrations were highest in samples taken up to 3 h after completing the work task. Regression analysis showed that workers who sprayed the day before the sampling task had higher glyphosate concentrations in pre-task samples than those who did not spray the day before (p < 0.01). Similarly, workers who took breaks during the work task had higher peak urinary glyphosate concentrations (p < 0.01). The multivariate mixed effect model showed that the following first morning void samples were approximately a factor 0.7 lower than post-task values. CONCLUSION: Occupational exposures to glyphosate among amenity horticulturalists are greater than those reported in environmental studies and comparable with previously reported agricultural studies. A suitable sampling strategy for occupational exposures to glyphosate is the collection of a spot urine sample up to 3 h after completing the application of a glyphosate based pesticide product, which provides a reliable marker of peak exposure.

Glyphosate in Irish adults - A pilot study in 2017.

OBJECTIVES: Glyphosate is the highest volume herbicide used globally and has recently been classified as a 2 A 'probably carcinogenic to humans' by the International Agency for Research on Cancer (IARC). There is limited data to evaluate the public health impacts from glyphosate exposure. The objective of this study is to conduct an exploratory glyphosate exposure assessment study among Irish adults, who were non-occupational users of glyphosate. STUDY DESIGN: A convenient sampling method was used, collecting one first morning void spot urine sample from each participant. METHODS: A biomonitoring survey involving the collection and analysis of 20 ml spot urine samples from 50 Irish adults was conducted in June 2017. Participants completed a short questionnaire to collect information on demographics, dietary habits and lifestyle. Glyphosate was extracted using solid phase extraction (SPE) and analysed by liquid chromatography tandem mass spectrometry (LC-MC/MS). RESULTS: Of the 50 urine samples analysed, 10 (20%) contained detectable levels of glyphosate (0.80-1.35 µg L-1). Exposure concentrations are higher than those reported in comparable studies of European and American adults. CONCLUSIONS: Glyphosate was detectable in 20% of the samples collected from Irish adults. The low proportion of detectable glyphosate levels could be due to lower localised use of pesticides, having a small sample size or the higher analytical detection limit used in this study (0.5 µg L-1), which could underestimate the true exposure and warrants further investigation. Given the widespread use of glyphosate, further information on population exposure is required to advance our understanding of the relationship between chronic low dose exposure to glyphosate and human health risk.

Exposure assessment using human biomonitoring for glyphosate and fluroxypyr users in amenity horticulture.

BACKGROUND: Pesticides and their potential adverse health effects are of great concern and there is a dearth of knowledge regarding occupational exposure to pesticides among amenity horticulturalists. OBJECTIVE: This study aims to measure occupational exposures to amenity horticuturalists using pesticides containing the active ingredients, glyphosate and fluroxypyr by urinary biomonitoring. METHODS: A total of 40 work tasks involving glyphosate and fluroxypyr were surveyed over the period of June - October 2015. Workers used a variety of pesticide application methods; manual knapsack sprayers, controlled droplet applicators, pressurised lance applicators and boom sprayers. Pesticide concentrations were measured in urine samples collected pre and post work tasks using liquid chromatography tandem mass spectrometry (LC-MS/MS). Differences in pesticide urinary concentrations pre and post work task, and across applications methods were analysed using paired t-tests and linear regression. RESULTS: Pesticide urinary concentrations were higher than those reported for environmental exposures and comparable to those reported in some agricultural studies. Log-transformed pesticide concentrations were statistically significantly higher in post-work samples compared to those in pre-work samples (paired t-test, p<0.001; for both µgL-1 and µmol/mol creatinine). Urinary pesticide concentrations in post-work samples had a geometric mean (geometric standard deviation) of 0.66 (1.11) µgL-1 for glyphosate and 0.29 (1.69) µgL-1 for fluroxypyr. Linear regression revealed a statistically significant positive association to exist between the time-interval between samples and the log-transformed adjusted (i.e. post- minus pre-task) pesticide urinary concentrations (ß=0.0039; p<0.0001). CONCLUSION: Amenity horticulturists can be exposed to pesticides during tasks involving these products. Further research is required to evaluate routes of exposure among this occupational group.