Definitions of monitoring activities and their relevance for the practice of occupational health

HBM4EU Occupational Biomonitoring Study on e-Waste-Study Protocol

Workers involved in the processing of electronic waste (e-waste) are potentially exposed to toxic chemicals. If exposure occurs, this may result in uptake and potential adverse health effects. Thus, exposure surveillance is an important requirement for health risk management and prevention of occupational disease. Human biomonitoring by measurement of specific biomarkers in body fluids is considered as an effective method of exposure surveillance. The aim of this study is to investigate the internal exposure of workers processing e-waste using a human biomonitoring approach, which will stimulate improved work practices and contribute to raising awareness of potential hazards. This exploratory study in occupational exposures in e-waste processing is part of the European Human Biomonitoring Initiative (HBM4EU). Here we present a study protocol using a cross sectional survey design to study worker’s exposures and compare these to the exposure of subjects preferably employed in the same company but with no known exposure to industrial recycling of e-waste. The present study protocol will be applied in six to eight European countries to ensure standardised data collection. The target population size is 300 exposed and 150 controls. Biomarkers of exposure for the following chemicals will be used: chromium, cadmium and lead in blood and urine; brominated flame retardants and polychlorobiphenyls in blood; mercury, organophosphate flame retardants and phthalates in urine, and chromium, cadmium, lead and mercury in hair. In addition, the following effect biomarkers will be studied: micronuclei, epigenetic, oxidative stress, inflammatory markers and telomere length in blood and metabolomics in urine. Occupational hygiene sampling methods (airborne and settled dust, silicon wristbands and handwipes) and contextual information will be collected to facilitate the interpretation of the biomarker results and discuss exposure mitigating interventions to further reduce exposures if needed. This study protocol can be adapted to future European-wide occupational studies.

The use of biomarkers in occupational health research, practice, and policy

Biomarkers are potentially useful tools for occupational health and safety research, practice, and policy. However, the full realization of this potential has not been achieved. In this paper, the progress made in these three usage areas is reviewed to identify what efforts can be taken to realize the full promise of biomarkers. Biomarker uses are described by a diverse taxonomy that builds on the categories of exposure, effect and susceptibility, and the continuum between exposure and disease prognosis. The most significant uses of biomarkers in occupational health have been in biological monitoring of workers. Other important uses have been in enhancing research and assessing mechanisms of action of occupational toxicants at low exposures. Seven critical areas will influence the extent to which the potential of biomarkers in occupational health and safety is realized. These include: (1) adequate investment in validation; (2) obtaining international agreement on exposure guidelines; (3) exploring the utility of biomarkers in regulation; (4) applying biomarkers to critical occupational safety and health questions; (5) developing the exposome; (6) utilizing biomarkers to address emerging occupational health issues; and (7) continuing to address the ethical and social justice issues related to biomarkers. Overall, if biomarkers are to make a major contribution to occupational health and safety then a more holistic approach to bringing them from the laboratory to practice will be needed.

Analyses of representative biomarkers of exposure and effect by chromatographic, mass spectrometric, and nuclear magnetic resonance techniques: method development and application in life sciences

Biomarkers are essential tools in monitoring studies, which include environmental monitoring, biological monitoring, biological effect monitoring, and health surveillance, as well as drug development processes. Their discovery, validation, and analysis require highly sensitive and selective analytical technologies. In this regard, gas and liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy have facilitated great achievements in all these areas. In addition and closely related to biomarkers, the ongoing developments in these techniques promise a better understanding of the nature and mechanisms of toxic effects originating from various chemical, biological, or physical sources. This Review compiles studies performed on selected biomarkers with respect to both method development and application. Section 1 summarizes the concept of biomarkers; their application in various industrial/occupational, agricultural, drug developmental, and medical/clinical platforms. This section also focuses on biotransformation studies in close relation to biomarker discovery and validation, and on major techniques utilized in this area. In Section 2, biotransformation of volatile anesthetics in humans with a focus on mercapturic acid derivatives as potential biomarkers of effect is reviewed. The use of GC-ECD, GC/MS, and 19F-NMR in these studies is described. Section 3 focuses on the analysis of aldehydic lipid peroxidation degradation products by GC-ECD in mammalian cells in which oxidative stress induced chemically, and in humans after various challenges; anesthetic exposure, ischemia-reperfusion, and controlled endurance exercise. In Section 4, method development for protein and DNA oxidation products by LC-tandem MS and its application in mammalian cells and in humans are summarized. Possibilities, limitations, and future perspectives are discussed in Section 5.

Biological monitoring of exposure to mixtures

This short review is aimed at establishing general principles of biological monitoring for chemical mixtures. When interactions occur, they appear to be toxicokinetic in nature, often resulting from competition between two or more substances for the same biotransformation enzymes. A threshold is frequently observed for such an interaction, so that it might not influence the relationship between the absorbed dose and the value of the relevant biomarker. The extent of the interaction between pairs of chemicals also depends on the extent of biotransformation of each compound. As a result, the measurement of the parent compound or its metabolite will be differentially influenced by the presence of an interfering chemical. Biological limit values (BLV) are often established from the correlation between the bioindicator concentration in a given biological medium and the airborne concentration of the parent compound. When this relationship is derived from exposure to pure chemicals, it might not always yield an appropriate BLV for monitoring exposure to a mixture that includes this particular chemical. Under certain conditions such as the stability of mixture composition, a single biomarker such as 1-hydroxypyrene in PAH exposure can be used to reflect the overall exposure to a mixture. Finally, there is clearly a need for a greater research effort on the toxicology of mixtures to make biological monitoring a useful tool in occupational health.

Analysis of ethenoguanine adducts in human urine using high performance liquid chromatography-tandem mass spectrometry

Several chemical carcinogens, such as vinyl chloride and ethyl carbamate, can react with DNA to form etheno-adducts in vitro and in vivo, which can be repaired through the base excision repair pathway, and then excreted with the urine. A specific and sensitive method, based on high performance liquid chromatography electrospray ionization tandem mass spectrometry, was developed for the detection of ethenoguanines (1,N2-ethenoguanine and its isomer N2,3 ethenoguanine) in urine. Urine samples were obtained from 13 healthy subjects not occupationally exposed to industrial chemicals. A confirmatory GC/MS method was also applied. Ethenoguanine isomers excreted with the urine were in the low nmol/l range (<0.3-8 nmol/l). Since occupational exposure to chemicals that may form etheno-adducts can be ruled out, endogenously produced intermediates, such as 2,3-epoxy-4-hydroxynonanal, may be responsible for the formation of etheno-adducts in human DNA. The background level of the general population has to be taken into account, especially in the investigation of persons occupationally exposed to etheno-adduct forming chemicals.

Serum beta-glucuronidase activity in a population of ex-coalminers

BACKGROUND

The aim of this study was to investigate whether BGD activity is of additional value in the assessment of pulmonary inflammation caused by coal dust exposure.

DESIGN AND METHODS

Ex-coalminers were included in this study. Forty-eight healthy male subjects, without a relevant medical history, were used as controls.

RESULTS

In ex-coalminers serum BGD activity was higher compared to the control group. Moreover, ex-coalminers with a normal chest radiograph and normal serum LDH demonstrated elevated serum BGD compared to the control group. However, no relation was found in the total group of ex-coalminers between serum BGD activity and pulmonary function parameters.

CONCLUSIONS

Our study adds in vivo human evidence to the already existing animal data that BGD is a potential biomarker useful in monitoring pulmonary inflammation caused by coal dust exposure.

Role of individual susceptibility in risk assessment of pesticides

OBJECTIVES

This study presents criteria for assessing the individual pesticide burden of workers in the chemical industry.

METHODS

A group of 1003 workers exposed to methylparathion or ethylparathion (alkyl phosphates), propoxur (carbamate), or cyfluthrin (pyrethroid) was investigated. After exposure to methylparathion or ethylparathion the methylparathion or ethylparathion and methylparaoxon or ethylparaoxon concentrations in plasma, the p-nitrophenol concentration in urine, and the activities of cholinesterase and acetylcholinesterase were measured. For exposure to propoxur the propoxur concentration in plasma, the 2-isopropoxyphenol concentration in urine, and the cholinesterase and acetylcholinesterase activities were measured. For exposure to cyfluthrin the cyfluthrin concentration in plasma was measured.

RESULTS

At the same propoxur concentration only workers with a low individual acetylcholinesterase activity reported symptoms. Workers who metabolised cyfluthrin rapidly reported less symptoms than workers with a lower rate of metabolism. This tendency was also evident in cases of mixed exposure (cyfluthrin and methylparathion).

CONCLUSIONS

In the assessment of exposure to pesticides susceptibility of the individual person has to be considered.

Consideration of individual susceptibility in adverse pesticide effects

The modern environmental awareness leads to the realisation that the human metabolism is stressed by a huge number of chemical substances. Generally, these background exposures, consisting predominantly from natural and partly from industrial as well as life style sources, are tolerated without any adverse effects. Pesticides are chemicals intentionally introduced to the environment and have become necessities in modern agriculture as well as in indoor pest control. Their residues, therefore, is attracting more and more concern. For the majority of pesticides neither occupational nor environmental medical risk evaluations are so far available. Therefore, at the moment the occupational as well as the environmental supported preventive concept may only be achieved, if binding instructions upon experience and guide values are developed for the assessment of the individual risk of handling pesticides. In the occupational and environmental pesticide prophylaxis the ubiquitous background exposure levels in consideration with individual susceptibility factors should be recommended as provisional biological tolerance guide values. The suitability of this guide values concept for pesticides is demonstrated by determining the background exposure and the biomarkers of susceptibility of 250 unexposed persons as well as of more than 1200 occupationally exposed persons. As a result, a significant dependence of their health fidelity from the background exposure profile impressed on the individual polymorphism of the key enzymes was observed. Especially, the cumulative adducts of electrophilic substances and their metabolites with macromolecules like HSA and Hb turned out to be sensitive markers for the capacity of the individual metabolic rate. For alkylating and arylating pesticides the observed interindividual susceptibility to their adverse effects depends on the variability of the individual 'toxifying' and 'detoxifying' metabolic rates. Until scientific evaluation of official biological tolerance values for pesticides is carried out, it is advisable for risk prophylaxis to orientate the assessment of any individual tolerable stress and strain from pesticides to the synergism between background exposure, life style factors and biomarkers of specific susceptibility. They may be examined by a monitoring of conjugates and polymorphism marked by the individual metabolic rate. The monitoring and surveillance of pesticide exposures is mainly introduced by the recommendation of tolerable biological values from the reference value concept. This concept is an essential contribution to an objective risk discussion with regard to individual stress and strain profiles in environmental exposure scenarios.

Japanese experience in biological monitoring

In Japan, industrial health control is accomplished by control of the working environment, work practice management and health care. Periodical biomonitoring of workers exposed to lead and 8 popular organic solvents, including mixed solvents, became mandatory as of October 1, 1989, with an ordinance issued by the Ministry of Labor. This ordinance states that the results of measurements of lead and the 8 solvents in each work place must be classified into 3 categories, named distributions 1, 2 and 3 based on the biological level of the determinant, and then must be reported to the Labor Standards Inspection Office. Distribution 3 encompasses workers having concentration levels above the BEIs of ACGIH except for the concentration of lead in the blood. The National Federation of Industrial Health Organizations surveyed the state of biological monitoring in Japan by a questionnaire to the laboratories. The total number of cases examined in the fiscal year 1990 was about 110,000 for the biomonitoring of lead, and about 520,000 for the monitoring of urinary metabolites of the 8 organic solvents. The ratio of the number of workers in distribution 3 to that of the total workers examined was 0.4% for urinary delta aminolevulinic acid and 0.2-3.5% for the urinary metabolites of each organic solvent. Similar results were obtained from 7 major laboratories. To achieve large-scale biological monitoring in future, a method is necessary for evaluating the exposure or health risks of workers exposed to mixed organic solvents by estimating their urinary metabolites.

Identification and quantitative determination of a carboxylic and a mercapturic acid metabolite of etridiazole in urine of rat and man. Potential tools for biological monitoring

Etridiazole, 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole, was orally administered to rats and human volunteers. Two metabolites of etridiazole were synthesized: 5-ethoxy-1,2,4-thiadiazole-3-carboxylic acid (ET-CA) and N-acetyl-S-(5-ethoxy-1,2,4-thiadiazol-3-yl-methyl)-L-cysteine (ET-MA). Selective and sensitive analytical procedures to determine etridiazole, the carboxylic acid ET-CA and the mercapturic acid ET-MA in urine were developed. The detection limit of etridiazole, applying GC with nitrogen selective detection (GC-NPD), was 36 micrograms/l urine (CV = 15.4%, n = 3). The detection limit of ET-CA, applying GC with sulphur selective detection (GC-FPD), was 100 micrograms/l urine (CV = 9.8%, n = 3). In urine of rats orally treated with etridiazole, ET-CA and ET-MA were identified as metabolites of etridiazole, whereas in urine of humans given oral etridiazole, only ET-CA was identified. Unmetabolized etridiazole was excreted for less than 0.1% of the administered dose in rats. ET-CA, however, accounted for 22 +/- 9% of the administered dose of etridiazole in rats and for 13 +/- 6% in humans. ET-MA appeared to be a minor urinary metabolite of etridiazole. ET-CA is proposed as a possible biomarker for the biological monitoring of etridiazole.

Biological monitoring and medical screening at the workplace in the EC countries

Health surveillance in the work environment involves continuous biological monitoring and medical screening, with the purpose of primary and secondary prophylaxis of work-related diseases. Is this screening activity governed by a rationale based on knowledge of dangerous exposure and the availability of valid tests? In the USA, where health surveillance programmes are used extensively, a study has found screening activity to be associated more with plant size than which relevant exposure. This study was done to elucidate the character and extent of use of health surveillance in the work environment in the EC countries with the aid of a questionnaire survey. The chief medical officers of the National Labour Inspectorates supplied information on substances covered by health surveillance programme in the EC member states, together with the legislative status and numbers of exposed workers. Belgium, France, Italy and the former Federal Republic of Germany made extensive use of health surveillance programmes in cases of known exposure to metals, organic solvents, carcinogenic and genotoxic substances, mineral dust, ionizing radiation, and biological agents. Denmark and Holland ran national programmes only for substances covered by EC directives, while England, Ireland, Spain, and Portugal comprised an intermediate user group. The result suggest that the use of health surveillance is related more to the national choice of standard regulatory instruments than to relevant exposure.

Biological effect monitoring of occupational exposure to 1,3-dichloropropene: effects on liver and renal function and on glutathione conjugation

A prospective study was performed in the Dutch flower bulb culture to investigate the possible effects of subchronic exposure to the soil fumigant 1,3-dichloropropene (DCP) on liver and kidney function and on glutathione conjugation capacity in blood. Urine spot samples and venous blood samples from 14 workers applying DCP (applicators) were taken at the start of the season in July, and after the season in October. The parameters of liver function measured were: alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, gamma-glutamyltranspeptidase, and total bilirubin (conjugated and unconjugated). Total bilirubin was significantly decreased from 9.5 before to 7.0 mumol/l after the season. In combination with an increase in serum gamma-glutamyltranspeptidase activity from 12.5 to 19.5 U/l this indicates moderate hepatic enzyme induction. To study renal function, creatinine and beta 2-microglobulin in serum, and beta 2-microglobulin, albumin, alanine aminopeptidase, beta-galactosidase, and retinol binding protein in urine were measured. The glomerular function parameters albumin in urine and creatinine in serum changed significantly during the season: albumin concentration increased from 5.2 to 7.6 mg/l, whereas creatinine concentration [corrected] decreased from 93.0 to 87.5 mumol/l. The tubular function parameter retinol binding protein also increased in concentration from 20.0 to 26.9 micrograms/l. Therefore, a subclinical nephrotoxic effect of subchronic exposure to DCP cannot be excluded. Effects on glutathione conjugation capacity were studied by measuring erythrocyte glutathione S-transferase activity and blood glutathione concentrations. The activity of glutathione S-transferase in erythrocytes was significantly decreased from 4.7 before to 3.3 U/g haemoglobin after the season. The same was true for the blood glutathione concentrations, which decreased from 0.93 to 0.82 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of subacute oral intake of the food antioxidant butylated hydroxyanisole on clinical parameters and phase-I and -II biotransformation capacity in man

A study is presented in which eight healthy male non-smoking volunteers ingested a daily amount of 0.5 mg/kg butylated hydroxyanisole (BHA) for 10 consecutive days. Blood samples were taken on days -6 and 0 before and on days 4 and 7 after the first BHA administration for the assessment of standard clinical plasma parameters (L-aspartate aminotransferase, L-alanine-aminotransferase, L-gamma-glutamyltranspeptidase, creatine phosphokinase, lactate dehydrogenase, total protein, albumin, urea, creatinine, Na+, and Cl-). Antipyrine (500 mg p.o.) and paracetamol (500 mg p.o) were administered before and during BHA administration as test substances to measure phase-I and phase-II biotransformation capacity. Saliva samples and urine were subsequently collected for the assessment of kinetic parameters (e.g. saliva elimination half-life, saliva clearance, apparent volume of distribution) and urinary excretion of metabolites. Kinetic plasma parameters of BHA itself were determined in plasma samples obtained via a catheter in an arm vein after oral BHA intake on days 0 and 7. Levels of antipyrine, paracetamol, BHA and metabolites in plasma, saliva or urine were quantified by standard or newly developed reversed-phase high-performance liquid chromatography methods. Urinary excretion of Na+, K+, and Cl-, as well as osmolality of urine were measured on three days before and six days during BHA administration. Generally, no significant differences were detected in the parameters measured, indicating that oral administration of BHA to men for 10 days remains without effects on clinical biochemical parameters and phase-I and phase-II biotransformation capacity. In contrast, urinary excretion of metabolites of BHA was significantly increased on days 3 and 7 vs. the first day of BHA administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Standard setting in occupational health: "philosophical" issues

This paper discusses various "philosophical" issues in standard setting in occupational and environmental health, i.e., general principles, actual procedures for standard setting, inter- and intra-agency discrepancies in procedures and criteria, and choices and decisions in the preparation of criteria documents and in the evaluation of the toxicology databases. Unpublished, possibly confidential information should be made available to expert committees, workers, and the general public. There is an urgent need to improve the validity of the toxicology databases that have to underpin occupational and environmental exposure limits. Standard setting requires various ethically loaded choices and decisions by experts, employees, managers, government officials, and politicians.

Biological markers of solvent exposure

The important limitation of many epidemiologic studies is the relative inaccuracy of the assessment of the magnitude of exposure. For some solvents, the concentration in biological media is an indication of the internal exposure and is an indirect indication of the health risk, at least for acute effects. For long-term effects, e.g., carcinogenicity, biological monitoring data can also be used as showed with the individual occupational data on the level of trichloroacetic acid (TCA) in urine. Occupational epidemiology can improve the methods for the assessment of the actual total exposure and health risk in environmental epidemiology by providing higher dose cohort data.