Human biomonitoring reference values: Differences and similarities between approaches for identifying unusually high exposure of pollutants in humans

A revised concept for deriving reference values for internal exposures to chemical substances and its application to population-representative biomonitoring data in German children and adolescents 2014-2017 (GerES V)

HBM reference values, in contrast to toxicologically derived values, are statistically derived values that provide information on the exposure of the population. The exceedance frequency (if applicable for individual population groups) is often a first assessment standard for the local exposure situation for municipalities. More than 25 years have passed since the German Human Biomonitoring Commission (HBMC) formulated the first recommendations for the derivation of population-based reference values (HBM reference values, RV95) for substance concentrations based on HBM studies. A fundamental revision is timely, for several reasons. There have been considerable advances in relevant statistical methods, which meant that previously time-consuming and inaccessible procedures and calculations are now widely available. Furthermore, not all steps for the derivation of HBM reference values were clearly elaborated in the first recommendations. With this revision we intended to achieve a rigorous standardization of the entire process of deriving HBM reference values, also to realise a higher degree of transparency. In accordance with established international practice, it is recommended to use the 95th percentile of the reference distribution as the HBM reference value. To this end, the empirical 95th percentile of a suitable sample should be rounded, ensuring that the rounded value is within the two-sided 95% confidence interval of the percentile. All estimates should be based on distribution-free methods, and the confidence interval should be estimated using a bootstrap approach, if possible, according to the BCa ("bias-corrected and accelerated bootstrap"). A minimum sample size of 80 observations is considered necessary. The entire procedure ensures that the derived HBM reference value is robust against at least two extreme values and can also be used for underlying mixed distributions. If it is known in advance that certain subgroups (different age groups, smokers, etc.) show differing internal exposures, it is recommended that group-specific HBM reference values should be derived. Especially when the sample sizes for individual subgroups are too small, individual datasets with potential outliers can be excluded in advance to homogenize the reference value population. In the second part, new HBM reference values based on data of the German Environmental Survey for Children and Adolescents (GerES V, 2014-2017) were derived in accordance with the revised recommendations. The GerES V is the most recent population-representative monitoring of human exposure to pollutants in Germany on children and adolescents aged 3-17 years (N = 2294). RV95 for GerES V are reported for four subgroups (males/females and 3-11/12-17 years) for 108 different substances including phthalates and alternative plasticisers, metals, organochlorine pesticides, polychlorinated biphenyls (PCB), per- and polyfluoroalkyl substances (PFAS), parabens, aprotic solvents, chlorophenols, polycyclic aromatic hydrocarbons (PAH) and UV filter, in total 135 biomarkers. Algorithms implemented in R were used for the statistics and the determination of the HBM reference values. To facilitate a quality control of the study data, the corresponding R source code is given, together with graphical representations of results. The HBM reference values listed in this article replace earlier RV95 values derived by the HBMC for children and adolescents from data of precedent GerES studies (e.g. published in Apel et al., 2017).

Human biomonitoring reference values, exposure distribution, and characteristics of metals in the general population of Taiwan: Taiwan environmental survey for Toxicants (TESTs), 2013-2016

Human biomonitoring (HBM) provides information to identify chemicals that need to be assessed regarding potential health risks to human populations. We established a population-representative sample in Taiwan, namely the Taiwan Environmental Survey for Toxicants (TESTs) in 2013-2016. In total, 1871 participants (aged 7-97 years) were recruited from throughout Taiwan. A questionnaire survey was applied to obtain individuals' demographic characteristics, and urine samples were obtained to assess metal concentrations. Inductively coupled plasma-mass spectrometry was used to determine concentrations of urinary As (total), Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Ni, Pb, Se, Sr, Tl, and Zn. The purpose of this study was to establish the human urinary reference levels (RVs) for metals in the general population of Taiwan. We found that median concentrations of urinary Cu, Fe, Pb, and Zn in males were statistically significant (p < 0.05) higher than in females (Cu: 11.48 vs. 10.00 μg/L; Fe: 11.48 vs. 10.46 μg/L; Pb: 0.87 vs. 0.76 μg/L; and Zn: 448.93 vs. 348.35 μg/L). On the contrary, Cd and Co were significantly lower in males than in females (Cd: 0.61 vs. 0.64 μg/L; and Co: 0.27 vs. 0.40 μg/L). Urinary Cd levels in the ≥18-year-old group (0.69 μg/L) were significantly higher than those in the 7-17-year-old group (0.49 μg/L, p < 0.001). Among the investigated metals, most were significantly higher in the 7-17-year-old group than in the ≥18-year-old group, except for Cd, Ga, and Pb. Participants who lived in central Taiwan had higher median levels of urinary Cd, Cu, Ga, Ni, and Zn than those in other regions. Median levels of urinary As, Cd, Pb, and Se were significantly higher in participants who lived in harbor (94.12 μg/L), suburban (0.68 μg/L), industrial (0.92 μg/L), and rural (50.29 μg/L) areas, respectively, than the others who lived in other areas. RV₉₅ percentiles of urinary metals (ng/mL) for 7-17/≥18-year-old groups were As (346.9/370.0), Cd (1.41/2.21), Co (2.30/1.73), Cr (0.88/0.88), Cu (28.02/22.78), Fe (42.27/42.36), Ga (0.13/0.12), In (0.05/0.04), Mn (3.83/2.91), Ni (8.09/6.17), Pb (8.09/5.75), Se (122.4/101.9), Sr (556.5/451.3), Tl (0.57/0.49), and Zn (1314.6/1058.8). In this study, we have highlighted the importance of As, Cd, Pb, and Mn exposure in the general population of Taiwan. The established RV₉₅ of urinary metals in Taiwanese would be fundamental information to promote the reduction of metal exposure or policy intervention. We concluded that urinary levels of exposure to certain metals in the general Taiwanese population varied by sex, age, region, and urbanization level. References of metal exposure in Taiwan were established in the current study.

Application of human biomonitoring data to support policy development, raise awareness and environmental public health protection among countries within the HBM4EU project

Most countries have acknowledged the importance of assessing and quantifying their population's internal exposure from chemicals in air, water, soil, food and other consumer products due to the potential health and economic impact. Human biomonitoring (HBM) is a valuable tool which can be used to quantify such exposures and effects. Results from HBM studies can also contribute to improving public health by providing evidence of individuals' internal chemical exposure as well as data to understand the burden of disease and associated costs thereby stimulating the development and implementation of evidence-based policy. To have a holistic view on HBM data utilisation, a multi-case research approach was used to explore the use of HBM data to support national chemical regulations, protect public health and raise awareness among countries participating in the HBM4EU project. The Human Biomonitoring for Europe (HBM4EU) Initiative (https://www.hbm4eu.eu/) is a collaborative effort involving 30 countries, the European Environment Agency (EEA) and the European Commission (contracting authority) to harmonise procedures across Europe and advance research into the understanding of the health impacts of environmental chemical exposure. One of the aims of the project was to use HBM data to support evidence based chemical policy and make this information timely and directly available for policy makers and all partners. The main data source for this article was the narratives collected from 27 countries within the HBM4EU project. The countries (self-selection) were grouped into 3 categories in terms of HBM data usage either for public awareness, policy support or for the establishment HBM programme. Narratives were analysed/summarised using guidelines and templates that focused on ministries involved in or advocating for HBM; steps required to engage policy makers; barriers, drivers and opportunities in developing a HBM programme. The narratives reported the use of HBM data either for raising awareness or addressing environmental/public health issues and policy development. The ministries of Health and Environment were reported to be the most prominent entities advocating for HBM, the involvement of several authorities/institutions in the national hubs was also cited to create an avenue to interact, discuss and gain the attention of policy makers. Participating in European projects and the general population interest in HBM studies were seen as drivers and opportunities in developing HBM programmes. A key barrier that was cited by countries for establishing and sustaining national HBM programmes was funding which is mainly due to the high costs associated with the collection and chemical analysis of human samples. Although challenges and barriers still exist, most countries within Europe were already conversant with the benefits and opportunities of HBM. This article offers important insights into factors associated with the utilisation of HBM data for policy support and public awareness.

Interpreting biomonitoring data: Introducing the international human biomonitoring (i-HBM) working group's health-based guidance value (HB2GV) dashboard

Human biomonitoring (HBM) data measured in specific contexts or populations provide information for comparing population exposures. There are numerous health-based biomonitoring guidance values, but to locate these values, interested parties need to seek them out individually from publications, governmental reports, websites and other sources. Until now, there has been no central, international repository for this information. Thus, a tool is needed to help researchers, public health professionals, risk assessors, and regulatory decision makers to quickly locate relevant values on numerous environmental chemicals. A free, on-line repository for international health-based guidance values to facilitate the interpretation of HBM data is now available. The repository is referred to as the "Human Biomonitoring Health-Based Guidance Value (HB2GV) Dashboard". The Dashboard represents the efforts of the International Human Biomonitoring Working Group (i-HBM), affiliated with the International Society of Exposure Science. The i-HBM's mission is to promote the use of population-level HBM data to inform public health decision-making by developing harmonized resources to facilitate the interpretation of HBM data in a health-based context. This paper describes the methods used to compile the human biomonitoring health-based guidance values, how the values can be accessed and used, and caveats with using the Dashboard for interpreting HBM data. To our knowledge, the HB2GV Dashboard is the first open-access, curated database of HBM guidance values developed for use in interpreting HBM data. This new resource can assist global HBM data users such as risk assessors, risk managers and biomonitoring programs with a readily available compilation of guidance values.

HBM4EU chromates study - Usefulness of measurement of blood chromium levels in the assessment of occupational Cr(VI) exposure

Occupational exposures to hexavalent Chromium (Cr(VI)) can occur in welding, hot working stainless steel processing, chrome plating, spray painting and coating activities. Recently, within the human biomonitoring for Europe initiative (HBM4EU), a study was performed to assess the suitability of different biomarkers to assess the exposure to Cr(VI) in various job tasks. Blood-based biomarkers may prove useful when more specific information on systemic and intracellular bioavailability is necessary. To this aim, concentrations of Cr in red blood cells (RBC-Cr) and in plasma (P-Cr) were analyzed in 345 Cr(VI) exposed workers and 175 controls to understand how these biomarkers may be affected by variable levels of exposure and job procedures. Compared to controls, significantly higher RBC-Cr levels were observed in bath plating and paint application workers, but not in welders, while all the 3 groups had significantly greater P-Cr concentrations. RBC-Cr and P-Cr in chrome platers showed a high correlation with Cr(VI) in inhalable dust, outside respiratory protective equipment (RPE), while such correlation could not be determined in welders. In platers, the use of RPE had a significant impact on the relationship between blood biomarkers and Cr(VI) in inhalable and respirable dust. Low correlations between P-Cr and RBC-Cr may reflect a difference in kinetics. This study showed that Cr-blood-based biomarkers can provide information on how workplace exposure translates into systemic availability of Cr(III) (extracellular, P-Cr) and Cr(VI) (intracellular, RBC-Cr). Further studies are needed to fully appreciate their use in an occupational health and safety context.

Concept for the Evaluation of Carcinogenic Substances in Population-Based Human Biomonitoring

The Human Biomonitoring (HBM) Commission at the German Environment Agency holds the opinion that for environmental carcinogens for which no exposure levels can be assumed and are harmless to health, health-based guidance values corresponding to the classical definition of the HBM-I or HBM-II value cannot be established. Therefore, only reference values have been derived so far for genotoxic carcinogens from exposure data of the general population or subpopulations. The concept presented here opens up the possibility of performing health risk assessments of carcinogenic substances in human biomonitoring, and thus goes decisively beyond the purely descriptive statistical reference value concept. Using the presented method, quantitative dose descriptors of internal exposure can be derived from those of external exposure, provided that sufficient toxicokinetic information is available. Dose descriptors of internal exposure then allow the simple estimate of additional lifetime cancer risks for measured biomarker concentrations or, conversely, of equivalent concentrations for selected risks, such as those considered as tolerable for the general population. HBM data of chronic exposures to genotoxic carcinogens can thus be used to assess the additional lifetime cancer risk referring to the general population and to justify and prioritize risk management measures.

Impacts of dietary exposure to pesticides on faecal microbiome metabolism in adult twins

BACKGROUND

Dietary habits have a profound influence on the metabolic activity of gut microorganisms and their influence on health. Concerns have been raised as to whether the consumption of foodstuffs contaminated with pesticides can contribute to the development of chronic disease by affecting the gut microbiome. We performed the first pesticide biomonitoring survey of the British population, and subsequently used the results to perform the first pesticide association study on gut microbiome composition and function from the TwinsUK registry.

METHODS

Dietary exposure of 186 common insecticide, herbicide, or fungicide residues and the faecal microbiome in 65 twin pairs in the UK was investigated. We evaluated if dietary habits, geographic location, or the rural/urban environment, are associated with the excretion of pesticide residues. The composition and metabolic activity of faecal microbiota was evaluated using shotgun metagenomics and metabolomics respectively. We performed a targeted urine metabolomics analysis in order to evaluate whether pesticide urinary excretion was also associated with physiological changes.

RESULTS

Pyrethroid and/or organophosphorus insecticide residues were found in all urine samples, while the herbicide glyphosate was found in 53% of individuals. Food frequency questionnaires showed that residues from organophosphates were higher with increased consumption of fruit and vegetables. A total of 34 associations between pesticide residue concentrations and faecal metabolite concentrations were detected. Glyphosate excretion was positively associated with an overall increased bacterial species richness, as well as to fatty acid metabolites and phosphate levels. The insecticide metabolite Br2CA, reflecting deltamethrin exposure, was positively associated with the phytoestrogens enterodiol and enterolactone, and negatively associated with some N-methyl amino acids. Urine metabolomics performed on a subset of samples did not reveal associations with the excretion of pesticide residues.

CONCLUSIONS

The consumption of conventionally grown fruit and vegetables leads to higher ingestion of pesticides with unknown long-term health consequences. Our results highlight the need for future dietary intervention studies to understand effects of pesticide exposure on the gut microbiome and possible health consequences.

Using Human Biomonitoring Data to Support Risk Assessment of Cosmetic Ingredients—A Case Study of Benzophenone-3

Safety assessment of UV filters for human health by the Scientific Committee on Consumer Safety (SCCS) is based on the estimation of internal dose following external (skin) application of cosmetic products, and comparison with a toxicological reference value after conversion to internal dose. Data from human biomonitoring (HBM) could be very useful in this regard, because it is based on the measurement of real-life internal exposure of the human population to a chemical. UV filters were included in the priority list of compounds to be addressed under the European Human Biomonitoring Initiative (HBM4EU), and risk assessment of benzophenone-3 (BP-3) was carried out based on HBM data. Using BP-3 as an example, this study investigated the benefits and limitations of the use of external versus internal exposure data to explore the usefulness of HBM to support the risk assessment of cosmetic ingredients. The results show that both approaches did indicate a risk to human health under certain levels of exposure. They also highlight the need for more robust exposure data on BP-3 and other cosmetic ingredients, and a standardized framework for incorporating HBM data in the risk assessment of cosmetic products.

Health Risk Assessment of Trace Metals Through Breast Milk Consumption in Saudi Arabia

We previously measured the levels of inorganic mercury, methylmercury, lead, cadmium, and manganese in the breast milk of 203 healthy Saudi mothers who participated in a cross-sectional study between 2011 and 2013. The current study aimed to (1) calculate reference values (RVs) for these metals in breast milk based on the 95th percentile of the metal and the corresponding 95% confidence interval following the approach of the German Human Biomonitoring Commission, and (2) assess the health risk associated with these metals (except lead) by determining the hazard quotient (HQ) and hazard index (HI) for breastfed infants. The risk characterization for the lead was applied using the margin of exposure (MOE) approach. Moreover, the cancer risk (CR) associated with lead was calculated. The RV₉₅s (percentage of samples for which the value was higher than the set value) for inorganic mercury, methylmercury, total mercury, cadmium, lead, and manganese in breast milk (μg/L) were 1.5 (7.9%), 1.5 (5.4%), 2.8 (8.9%), 2.5 (8.4%), 53 (11.3%), and 22.3 (11.8%) μg/L, respectively. The methylmercury, lead, and manganese levels in the present study were higher than those reported previously. The HQ for methylmercury greater than 1 was found in 68.5% of the samples, indicating there may be a potential non-carcinogenic health risk of infant exposure to the toxic metal via breast milk consumption. Despite the high cadmium and manganese levels in breast milk, our results suggested no health risk (HQ < 1). The HI representing the combined non-carcinogenic health risk of four metals was > 1, with methylmercury (74%) being the major contributor. The estimated MOE mean value of 0.134, less than 1, indicates that our breastfed infants may be at increased risk of neurodevelopmental impairments. The CR for lead in two infants was higher than the acceptable level of 1 × 10^-4. Although our results may suggest potential carcinogenic and non-carcinogenic risks of infant exposure to toxic metals through breast milk consumption, the benefits of breastfeeding are well recognized and outweigh the potential risks.

Italian Children Exposure to Bisphenol A: Biomonitoring Data from the LIFE PERSUADED Project

A human biomonitoring (HBM) study on bisphenol A (BPA) in Italian children and adolescents was performed within the LIFE PERSUADED project, considering the residing areas, sex and age. The median urinary BPA level was 7.02 µg/L, with children living in the South of Italy or in urban areas having higher levels than those residing in the North or in rural areas. Children aged 4–6 years had higher BPA levels than those aged 7–10 and 11–14 years, but no differences were detected between sexes. The exposure in Italian children was higher compared to children from other countries, but lower than the HBM guidance value (135 µg/L). The estimated daily intake was 0.17 μg/kg body weight (bw) per day, about 24-fold below the temporary Tolerable Daily Intake of 4 μg/kg bw per day established by the European Food Safety Authority. However, this threshold was exceeded in 1.44% of the enrolled children, raising concern about the overall exposure of Italian young population.

Human biomonitoring reference values and characteristics of Phthalate exposure in the general population of Taiwan: Taiwan Environmental Survey for Toxicants 2013-2016

Since a 2011 incident involving phthalate-tainted food, Taiwanese people have become concerned with food quality, and they are still being exposed to certain levels of phthalates. However, no nationwide human biomonitoring survey had been conducted to gather information on levels or reference values (RVs) of phthalates in the Taiwanese population. We aimed to establish the urinary levels and RVs of phthalate metabolites and identify exposure characteristics among Taiwan's population. We enrolled 1857 participants 7 years of age and older from the Taiwan Environmental Survey for Toxicants (TESTs) conducted during 2013-2016. Levels of 11 phthalate metabolites in each participant's urine samples were determined using liquid chromatography-tandem mass spectrometry. For all phthalate metabolites except for mono-methyl phthalate (MMP), mono-ethyl phthalate (MEP), and mono-ethylhexyl phthalate (MEHP), urinary median levels were significantly higher in the 7-17-year old group than in the ≧18-year-old group. For most phthalate metabolites and in the general population, the geometric mean decreased with increasing age. Median levels of MEP (19.55 μg/L), mono-benzyl phthalate (MBzP) (2.11 μg/L), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) (22.82 μg/L), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEOHP) (16.08 μg/L), ΣDibutyl phthalate metabolites (ΣDBPm) (0.17 nmol/mL), Σdi-(2-ethylhexyl) phthalate metabolites (ΣDEHPm) (0.29 nmol/mL) were higher in participants from central Taiwan than those from other areas. The median level of DBP (ΣDBPm: 0.20 nmol/mL) was significantly higher in participants from harbor areas than those from other urbanization groups. The RV of the 95 percentile (P₉₅) for phthalate metabolites in the 7-17/≧18-year-old groups were 185.95/208.19 μg/L for MMP, 198.46/265.81 μg/L for MEP, 119.85/69.99 μg/L for mono-isononyl phthalate (MiBP), 165.19/204.32 μg/L for Mono-n-butyl phthalate (MnBP), 15.61/11.73 μg/L for MBzP, 62.09/59.23 μg/L for MEHP, 149.70/69.66 μg/L for MEHHP, 112.06/35.07 μg/L for MEOHP, 195.20/93.83 μg/L for mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), 45.66/27.69 μg/L for mono-(2-carboxymethylhexyl) phthalate (MCMHP), and 9.09/12.13 μg/L for mono-iso-nonyl phthalate (MiNP). We concluded that phthalate exposure of the general population in Taiwan varies by sex, age, region, and urbanization level. Exposure by the 7-17-year-old group to DMP, DBP, and DEHP in Taiwan remains higher than that of youth from other countries. RV of phthalate metabolites in Taiwan were established in the current study.

Biomonitoring of Bis(2-ethylhexyl)phthalate (DEHP) in Italian children and adolescents: Data from LIFE PERSUADED project

The Bis(2-ethylhexyl)phthalate (DEHP), a widespread plasticizer, is considered an endocrine disrupting chemical with main toxicological effects on reproductive and metabolic systems. Human biomonitoring (HBM) studies are promoted to evaluate the background exposure levels. In the frame of LIFE PERSUADED project, the HBM study measured DEHP main metabolites (mono-(2-ethylhexyl) phthalate, MEHP; 2-ethyl-5-hydroxy-hexylphthalate, MEHHP; 2-ethyl-5-oxo-hexylphthalate, MEOHP) in Italian children and adolescent (4-14 years old) according to geographical macro-areas and areas, age and sex. Children from the South and the Centre of Italy showed higher median levels of DEHP, as a sum of its metabolites (48.14 and 47.80 μg/L), than those from the North (39.47 μg/L; p = 0.0090 and 0.0004, respectively). Considering the total population, boys are more exposed than girls (only as urinary volume), and children aged 4-6 years have higher median levels than those 7-10 and 11-14 years old. The derived reference values (RV95) for DEHP in children is 168 μg/L. The relative metabolic rates of DEHP, the background levels and, thus, the RV95, vary with the geographical area, age and sex, indicating that all these parameters should be considered in the risk assessment.

The reference values in the interpretation of toxicological data

The worldwide gradual expansion of industrialization has led to a dramatic increase in the production and use of chemical substances. This has resulted in a greater dispersion of these elements in the environment and in an increased exposure of the general population and workers. In this scenario, a thorough knowledge of exposure levels is needed in order to assess chemical risks in environmental and occupational settings. Biological monitoring is among the most useful tools for assessing exposure. However, in order to provide really effective guidance in the application/implementation of risk management measures, biomonitoring results need to be compared with appropriate references. Reference values (RVs) are an excellent resource since useful information for a correct interpretation of toxicological data can be obtained by comparing them with biomonitoring results. In the field of public health, this may enable us to identify potential sources of exposure, define the principal and most frequently exploited routes of exposure, and outline chemical absorption. Similarly, in occupational medicine, RVs can be used to give meaning to biomonitoring findings, especially when a biological limit value is not available for the chemical in question. Furthermore, these values are a valid tool for assessing exposure to chemical carcinogens. Therefore, by integrating reference values in an appropriate and complete system of guide values that also includes action levels and biological limit values, we could obtain both an adequate assessment of exposure and a better understanding of toxicological data.