New techniques for assessment of occupational respiratory diseases

Recently, as several studies have demonstrated, these non-invasive techniques, such as induced sputum (IS) or analysis of the exhaled air; exhaled nitric oxide (eNO) or exhaled breath condensate (EBC) provide fairly reliable results that correlate with those of "gold standard" methods (bronchoscopy, bronchoalveolar lavage) which are more invasive and uncomfortable for patients. Although novel approaches have attracted the attention of scientists, they have not been examined in relation to occupational settings and professional diseases. The IS is a useful biological medium for the diagnosis of occupational asthma and for the assessment of exposures to harmful dust at workplaces. The eNO analysis can serve as an easy and comfortable diagnostic tool for the professional asthma after exposure to various allergens. The examination of EBC biomarkers evaluates local doses of hard metals in the lung, as well as detection of oxidative stress markers (malondialdehyde, H2O2). Due to the need to standardize the procedures for EBC collection, further studies on EBC validation and the subsequent application in the clinical and epidemiological fields are required. The techniques listed in this article may serve as optimal tools for diagnosis of occupational respiratory diseases and for screening/monitoring programs following inhalation exposures in future (ref 64).

[Environmental and biological monitoring of exposure to polycyclic aromatic hydrocarbons in workers of an electric steel foundry]

AIMS

To assess and classify exposure to Polycyclic Aromatic Hydrocarbons (PAHs) in some specific working areas of a steel foundry operating with a continuous casting process and evaluate biomonitoring data in different job tasks.

METHODS

Exposure to dusts and six PAHs classified as carcinogenic by EU directives was studied in a cohort of 35 male foundry workers (aged 41.1 +/- 6.9 years), who were examined both prior to and at the end of the work-shift (06:00 a.m.-02:00 p.m.) in two different periods. The urinary excretion of 1-hydroxypyrene (1-OH-P) was measured as a biomarker of exposure to pyrene.

RESULTS

PAHs concentrations ranged from 461.8 to 935.6 ng/m3 near the continuous casting area, whereas lower values were measured near the ladle furnace. End of shift 1-OH-P values were higher in 11 non-smoking workers involved in continuous casting process as compared to those employed in mantenance and furnace areas (median of the second determination: 5.70 microg/g creatinine--range: 1.24-21.24 vs 1.17 microg/g creatinine--range: 0.23-4.49; p< 0.001). 1-OH-P excretion was significantly correlated with both the sum of six carcinogenic PAHs and pyrene airborne concentrations. In two biomonitoring sessions, 9.1% and 34.3% of the workers respectively showed end-of-shift 1-OH-P values exceeding the occupational exposure limit (OEL) (4.4 microg/g creatinine or 2.3 micromol/mol(-1) creatinine) recommended for coke-oven workers.

CONCLUSIONS

1-OH-P is a useful biomarker in assessing PAH exposure and is associated with job category at a Steelplant. Due to exposure variability, to assess risk associated with PAHs exposure, biological monitoring should be carried out periodically.

[Occupational Medicine Programme in the university degree on prevention techniques in living and working environments]

This document has been prepared by a working group of University Professors belonging to the Italian Society of Occupational Medicine and Industrial Hygiene, with the aim of defining the role of this discipline in the university course on Prevention Techniques in Working and Living Environments. The course trains health professionals to apply risk assessment techniques, preventive measures and legislative tools for safety and health in working and living environments, food and beverages hygiene, and Public Health. The document describes the organization and the structure of the course, general and specific learning objectives, occupational medicine teaching and other organization aspects. Also, training of non-graduate technicians working for local health authorities is discussed.

Glutathione S-transferases M1-1 and T1-1 as risk modifiers for renal cell cancer associated with occupational exposure to chemicals

AIMS

To investigate the possible interaction between occupational risk factors and genotype for glutathione S-transferases M1 and T1 (GSTM1 and GSTT1) in renal cell cancer (RCC).

METHODS

One hundred patients with RCC and 200 outpatient controls were enrolled at Parma University Hospital. The polymorphisms of glutathione S-transferase M1-1 (GSTM1) and T1-1 (GSTT1) were investigated by PCR; occupational history was collected by a structured questionnaire.

RESULTS

Subjects with GSTM1 present genotype showed higher risks for RCC, compared to GSTM1 null subjects, if exposed to metals (OR 2.73; 95% CI 0.91 to 8.22 v 1.14; 95% CI 0.46 to 2.82) or pesticides (OR 3.46; 95% CI 1.12 to 10.74 v 1.59; 95% CI 0.48 to 5.34). The GSTT1 present genotype also enhanced the risk (about twofold) of RCC among subjects exposed to solvents and pesticides, compared with those GSTT1 null.

CONCLUSIONS

Results support the hypothesis that GSTM1 and GSTT1 polymorphisms can interact with several occupational exposures to significantly modify the risk of RCC among exposed subjects.

[Indicators of pulmonary epithelial damage among workers at a foundry exposed to airborne pollutants]

Foundry ambient air contains very high concentrations of noxious substances, such as particulate matter and gaseous pollutants, which can target the respiratory epithelium. Serum concentrations of the 16-kDa Clara cell protein (CC16-S) may reflect both the integrity of the epithelial barrier and smoke-induced Clara cell toxicity. To evaluate whether CC16-S is a sensitive biomarker of early respiratory disturbances, it was determined in a group of 35 foundry male workers (aged 41.1 +/- 6.9 years) examined both prior to and at the end of their work-shift (06:00 a.m.-02:00 p.m.). Exposure to inhalable/respirable dusts and PAH was characterized; urinary excretion of 1-hydroxypyrene (1-OH-P) and naphtol was measured to assess exposure to pyrene and naphthalene, respectively. CC16 serum levels decreased at the end of the shift (10.7 +/- 3.82 micrograms/L vs. 8.39 +/- 3.05 micrograms/L; p < 0.01); such decrements were significantly larger in more exposed workers. Although smokers had lower baseline values as compared to non smokers, both subgroups showed an average decrease of 30% in CC16-S concentrations at the end of shift. CC16-S was also negatively correlated with 1-OH-P, but not with naphtol concentrations. Decreased CC16-S levels can result from citotoxicity and would represent an useful biomarker of pneumotoxicity in foundry workers exposed to complex mixtures.

[In vitro models for the evaluation of the neurotoxicity of methylmercury. Current state of knowledge]

BACKGROUND

In adults, MeHg poisoning is characterized by damage to discrete anatomical areas of the brain (visual cortex, loss of neurons from the granule layer of the cerebellum). However, the immature central nervous system (CNS), which is extremely sensitive to MeHg neurotoxicity, shows a diffuse and widespread damage disorganization of cerebral cortex cytoarchitecture, disappearance of granule cells with narrowing of the molecular layer. While adverse effects have been unequivocally demonstrated in poisoning incidents in humans (visual abnormalities, sensory impairment of the extremities, cerebellar ataxia, hearing loss, muscle weakness, tremor and mental deterioration), the implications of lower level exposures, such as those occurring in fish-eating populations, are still controversial. The high affinity of MeHg for thiol groups makes proteins and peptides bearing cysteines the predominant targets for structural and functional modification by MeHg in all subcellular compartments.

METHODS

The identification of MeHg cellular and sub-cellular targets in the CNS is complicated by the fact that it is difficult to observe the outcomes directly in vivo. In neurobiology, in vitro cell culture techniques have been successfully developed and employed to address specific questions of cell biology and nervous system functioning and provide a means to systematically study the complexity of cellular functions of the CNS elements. Moreover, they provide a convenient experimental tool for testing possible functions or postulates in vivo that otherwise might not be conducted.

RESULTS

Several mechanisms have been proposed as being implicated in the neurotoxic effects of MeHg. Examples of MeHg molecular effects which may be relevant to risk assessment are presented, including cell death mode, effects on microtubules, calcium signalling, oxidative stress, effects on neurotransmitter systems.

CONCLUSIONS

Molecular and cellular approaches permit exploration of early biological responses to chemical or physical agents and definition of the role of these early effects in altered cellular structure and function.

Occupational risk factors for renal cell cancer. An Italian case-control study

AIM

To examine possible associations between occupational and environmental risk factors and renal cell cancer (RCC), a tumour with unclear aetiology and increasing incidence.

METHODS

A questionnaire-based case-control study of 100 histologically verified cases of RCC and 200 controls was conducted at Parma University Hospital. The control group was enrolled from patients attending different outpatient departments and represented the same residential area as the cases. For all exposure variables under study, two levels of duration were defined: "short" and "prolonged" for less than 10 years or more, respectively.

RESULTS

The highest risk estimates for RCC were found for "prolonged" exposure to organic solvents with an odds ratio (OR) of 2.2 (95% confidence interval, CI: 1.0-4.8). "Prolonged" exposures to pesticides and copper sulphate were also associated with increased risk, OR 2.0 (95% CI: 0.8-4.7) and OR 2.7 (95% CI: 1.3-5.5), respectively.

CONCLUSIONS

Our data suggests an association between RCC and exposure to organic solvents, pesticides and copper sulphate. A risk gradient as a function of exposure duration was found for organic solvents (p = 0.044) and copper sulphate (p = 0.036), but not for pesticides.

Polymorphism of xenobiotic-metabolizing enzymes and excretion of styrene-specific mercapturic acids

The role of polymorphic xenobiotic-metabolizing enzymes in the interindividual variability of phenylhydroxyethyl mercapturic acids (PHEMAs) was investigated in 56 styrene-exposed workers. Ambient monitoring was carried out using passive personal samplers (geometric mean, 157 mg/m3 8-h time-weighted average; geometric standard deviation, 2.90). Biomonitoring was based on mandelic acid and phenylglyoxylic acid in urine spot samples collected at the end of the work shift ("end-of-shift") and prior to the subsequent shift ("next morning"). Four PHEMA diastereoisomers, namely (R,R)-M1, (S,R)-M1, (S,R)-M2, and (R,R)-M2, were determined by HPLC/tandem mass spectrometry. The genotypes of glutathione S-transferases M1-1 (GSTM1), T1-1 (GSTT1) and P1-1 (GSTP1), and microsomal epoxide hydrolase (EPHX) were characterized by PCR-based methods. Workers bearing the GSTM1pos genotype showed PHEMA concentrations five and six times higher (in end-of-shift and next-morning samples, respectively) as compared to GSTM1null people. In GSTM1pos subjects, (R,R)-M1 was the main mercapturate affected by the GSTM1 status, accounting for 54 and 68% of total PHEMAs in end-of-shift and next-morning samples, respectively. Compared to GSTM1null, GSTM1pos subjects excreted more -M1 than -M2 and more (R,R)-M1 and (S,R)-M2 than (S,R)-M1 and (R,R)-M2 diastereoisomers. Thus, GSTM1-1 is the main isoenzyme catalyzing GSH-conjugation of styrene-7,8-oxide in humans and it seems to act in a regio- and stereoselective way. PHEMAs cannot be recommended as biomarkers of exposure to styrene, unless the GSTM1 genotype is considered in data interpretation. Their role as biomarkers of susceptibility deserves further studies.

Determination of free and glucuronated hexane metabolites without prior hydrolysis by liquid- and gas-chromatography coupled with mass spectrometry

Since n-hexane metabolites are excreted as glucuronide conjugates, most conventional analytical procedures require preliminary hydrolysis, yielding to the 'total' 2,5-hexanedione (2,5-HD), but also giving rise to a number of artifacts. The whole pattern of n-hexane metabolites, both conjugated and unconjugated, as well as different methods of sample pretreatment have been evaluated by hyphenated techniques (liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS)). Aliquots of urine from rats exposed to n-hexane underwent enzymatic or acid hydrolysis or both; whereas one aliquot was applied to LC-MS, dichloromethane extracts were analyzed by GC-MS. In untreated urine, four glucuronides (-G) were identified and characterized by LC-MS: 2-hexanol-G, 5-hydroxy-2-hexanone-G, 4,5-dyhydroxy-2-hexanone-G, and 2,5-hexanediol-G. 'Free' 2,5-HD was detectable in non-hydrolyzed samples by both GC- and LC-MS. Whereas enzymatic hydrolysis did not increase the amount of 2,5-HD, acid hydrolysis led to increase 2,5-HD in variable amount and produced gamma-valerolactone as a result of a complete transformation of 4,5-dihydroxy-2-hexanone-G and the partial conversion from 5-hydroxy-2-hexanone-G. Further experiments showed that both 5-hydroxy-2-hexanone-G and 4,5-dihydroxy-2-hexanone-G, isolated by solid-phase extraction and hydrolyzed, yield comparable amount of 2,5-HD and gamma-valerolactone. In samples treated by acid hydrolysis, GC-MS only does not allow to understand the true source of 'total' 2,5-HD, which may be produced not only from 4,5-dihydroxy-2-hexanone-G but also from the more abundant 5-hydroxy-2-hexanone-G, which thus represents the main source of analytical artifacts. 'Free' 2,5-HD seems to be both suitable from an analytical point of view and meaningful for biological monitoring purposes, provided that conjugate metabolites are rapidly removed from the body leading to a negligible neurotoxic risk.

Determination of naphthalene metabolites in human urine by liquid chromatography-mass spectrometry with electrospray ionization

The use of a liquid chromatography-electrospray mass spectrometry system was investigated for the quantitative analysis of naphthalene metabolites (alpha-naphthol, alpha-naphthylglucuronide and beta-naphthylsulphate) in untreated urine samples. Chromatography was carried out under ion-suppressed reversed-phase conditions, by using high-speed (3 cm, 3 microns) columns and formic acid (2 mM) as a modifier in the mobile phase. The ionization was obtained in the negative-ion mode. Linearity, sensitivity and precision of the method were explored by operating in selected-ion monitoring mode. The method was applied to the quantitative analysis of naphthalene metabolites in untreated urine samples from workers in a naphthalene producing plant. Solid-phase extraction was used for sample clean-up and trace enrichment. Liquid chromatography-tandem mass spectrometry experiments were performed for confirmation purposes.

Peripheral markers of catecholaminergic dysfunction and symptoms of neurotoxicity among styrene-exposed workers

AIM

A cross-sectional investigation was carried out to assess possible relations between styrene-induced changes in three peripheral markers of catecholaminergic dysfunction and self-reported symptoms of neurotoxicity.

SUBJECTS

Male workers (n = 46) aged 14-60 (mean 29.5) years who had been exposed to styrene for an average of 6 (0.2-29) years were recruited in glassfiber reinforced plastics plants. A control group of 30 blue-collar workers aged 22-52 (mean 35) years and with no history of exposure to chemicals was recruited from local industries. Styrene exposure ranged from 5 to 120 ppm (8 h-TWA), the median level being relatively low (25 ppm, 8 h-TWA). Styrene metabolites, mandelic and phenylglycoxylic acids (MAPGA) in the "next morning" urine spot samples ranged from 32.0 to 931.1 mg/g creatinine (median 186.5).

METHODS

Platelet monoamine oxidases B (MAO B) and dopamine beta-hydroxylase (DBH) activities were assessed using methods based on HPLC and electrochemical detection. Plasma prolactin (PRL) was measured by a commercially available immunoassay. Questionnaire 16 (Q16) was used to survey self-reported symptoms.

RESULTS

Although there was no difference in DBH activity between exposed workers and controls, the most highly exposed workers had significantly lower activity than control subjects. A tendency to lower platelet MAO B activity in exposed than in control subjects was observed. The prevalence of plasma DBH and platelet MAO B values below the lower reference limit was similar in the two groups. PRL values exceeding the upper reference limit were higher (14/46 vs 2/30) among styrene-exposed workers, who also exhibited significantly higher median levels (10.0 vs 5.7 micrograms/l) than control subjects. Although the number of reported symptoms was similar among exposed and control subjects, in the exposed group it was positively associated with urinary MAPGA (Rho = 0.30, P = 0.04). Of the three peripheral markers of catecholaminergic dysfunction, plasma DBH was the only parameter negatively related to both urinary MAPGA (F = 9.56, P = 0.003) and the number of reported symptoms (Rho = 0.23, P = 0.05).

CONCLUSIONS

Plasma PRL appears to be a sensitive marker of styrene-induced tubero-infundibular dopaminergic dysfunction in male subjects. DBH in plasma and MAO B in platelets seem to be less suitable markers for biomonitoring effect at the individual level, although DBH was related to the number of reported symptoms and to internal dose. Further studies on a larger and more exposed population are necessary to clarify the significance of these markers for health and their predictive value with regard to both subjective disturbances and concurrently administered performance tests.

Peripheral markers of neurochemical effects among styrene-exposed workers

Monoamine oxidase B (MAO-B) activity in platelets, serum dopamine-beta-hydroxylase (DBH) activity, and serum prolactin (PRL) were measured during a cross-sectional investigation in workers occupationally exposed to styrene. The study group consisted of 53 workers (33 men and 20 women) employed for 9.3 years on average (range 1-22) in reinforced plastics plants. Sixty industrial workers with no known exposure to chemicals and comparable as to age, sex and confounding variables were recruited as controls. The activities of MAO-B in platelet-rich plasma and of DBH in serum from exposed and control subjects were measured within the same run, using methods based on the liquid-chromatographic determination of the reaction products. Serum PRL was determined by both EIA and RIA. Blood samples had been collected between 8:00 and 9:00 a.m. A lower DBH activity was found in exposed as compared to control workers (GM: 7.25 U/ml serum vs. 10.11 U/ml serum; p < 0.01), whereas MAO-B activity was significantly lower in a heavily exposed subgroup (10.1 vs. 13.8 U/10(7) platelets; p = 0.05), but not in the whole sample (p = 0.07). Serum PRL was higher both in male (GM: 8.90 ng/ml vs. 6.05 ng/ml; p < 0.01) and female (GM: 12.6 ng/ml vs. 9.33 ng/ml; p < 0.05) styrene-exposed workers as compared to their respective controls. Dose-response relationships were found for abnormally low DBH and abnormally high PRL values, with a threshold occurring at metabolite levels corresponding to 8h-TWA styrene concentrations in air around 25 ppm. In summary, this study shows that long-term exposure to relatively low levels of styrene can affect DBH activity and basal serum PRL. Owing to its sensitivity, PRL is a useful biomarker to show impairments of dopaminergic control on pituitary secretion. Since DBH is expression of catecholamine secretion, its decreased activity could represent an indirect index of altered turnover rate of the physiological substrate (i.e.dopamine) at the neuronal level. However, a direct interference by styrene metabolites on enzyme activity cannot be ruled out. Platelet MAO-B activity seems to be less sensitive to styrene exposure.

Age-related changes in interstitial norepinephrine. A microdialysis study in spontaneously hypertensive rats

This study was aimed at evaluating the time course of interstitial norepinephrine (NE) concentrations in the white adipose tissue and at assessing NE release after local perfusion with tyramine hydrochloride (TYR) in rats of different ages. Two groups of eight spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats, aged 14 to 16 weeks, were studied. The same animals were reexamined at the age of 52 to 54 weeks. A soft microdialysis probe was implanted subcutaneously in the parascapular region and was perfused with Ringer solution (flow rate: 2.0 microL/min). After an equilibration period, NE levels were monitored for 120 min, following which, TYR (0.1 nmol/min) was perfused for 90 min. Dialysates from each 30 min collection period were analyzed by HPLC using electrochemical detection. At 14 to 16 weeks, SHR showed higher NE concentrations in dialysates as compared to WKY (1124.0 pg/mL v 541.4 pg/mL; P < .001) and a blunted response to TYR challenge. The net output, estimated by subtracting basal values, was 86.0 pg NE/h in SHR as compared to 212.5 pg NE/ h in WKY (P = .005). Differences in basal NE levels persisted in the same aged groups (P < .001) as well as a blunted response to TYR. The net NE output was still lower in SHR as compared to WKY (320.4 pg NE/h v 414.7 pg NE/h in WKY; P = .023). Basal levels of NE in SHR could be accounted for by either a higher amount of the neurotransmitter stored into and released from vescicles or by an increased firing rate of the sympathetic fibers. Since TYR is known to deplete axoplasmic but not vesicular NE available for neurotransmission, the response of SHR to TYR challenge is consistent with an increased turnover rate of NE. Aging was associated with an increased response to TYR in both strains, thus suggesting an age-dependent decline in turnover rates or changes in NE reuptake mechanisms.

Development and validation of new screening tests for nephrotoxic effects

Within the framework of an European Commission-funded project, groups of industrial workers exposed to heavy metals (cadmium, mercury and lead) or solvents were studied together with corresponding control groups. Eighty-one measurements were carried out on urine and serum samples and the scientific results together with individual questionnaire information were entered into a central database. Data obtained was assessed centrally and individually in subsidiary studies. The measurable contributions were assessed either singly or in combination, of smoking, gender, metal exposure and site, to nephrotoxicity. The potential value of each test as an indicator of nephrotoxicity was then assessed on the basis of sensitivity and specificity. A number of new tests including prostaglandins and for extracellular matrix components were investigated as well as established tests for renal damage and dysfunction. The data obtained from this comprehensive study emphasises the value of noninvasive biomarkers for the early detection of nephrotoxicity due to environmental toxins. The urinary profile varied with the type of environmental/occupational toxin. By careful selection of a small panel of markers they can be used to indicate the presence of renal damage, the principal region affected, and to monitor the progress of disease and damage. Biomarkers were also used to confirm and tentatively establish safe exposure levels to nephrotoxins.

Serum prolactin in subjects occupationally exposed to manganese

To evaluate whether or not occupational exposure to manganese (Mn) affects basal levels of serum prolactin (PRL), a cross-sectional study was carried out in 31 occupationally-exposed workers, aged 39.2 years (DS 7.9) exposed to manganese (Mn) dusts for 14.5 years (range: 5 to 29 years) in a ferroalloy producing plant. Thirty-four industrial workers not exposed to neurotoxic chemicals and of comparable age composed the control group. Airborne Mn concentrations in dusts of the furnace area ranged 210 to 980 micrograms/m3, which is below the current American Conference of Governmental Industrial Hygienists (ACGIH)-recommended threshold limit value-time weighted average (TLV-TWA) of 1 mg/m3. Manganese concentrations in blood Mn (MnB) and in urine (MnU) were significantly higher in Mn-exposed workers as compared to control workers. The Mn-exposed workers showed significantly higher serum prolactin (PRL) levels with the geometric mean (GM) being 9.77 ng/ml with a geometric standard deviation (GSD) of 1.69 as compared to controls (GM 4.65 ng/ml, GSD 1.78, p < 0.001). Serum PRL was negatively related to age and positively correlated with both MnB and MnU. Dose-effect relationships were still significant in partial correlation analysis after control for age. The prevalence of abnormally high PRL values was consistent with a dose-response relationship. The observed increase in serum PRL among Mn-exposed workers suggests an impairment of tonic inhibition by tubero-infundibular dopaminergic neurons. The correlation between PRL and both MnB and MnU in samples collected at least 48 h from the last exposure suggests that such indices provide an estimation of the target dose.

Monitoring norepinephrine levels by microdialysis in the white adipose tissue of spontaneously hypertensive rats

1. To investigate whether microdialysis is suitable to monitor catecholamine in white adipose tissue of conscious rat and to assess eventual differences in norepinephrine (NE) interstitial levels, two groups of 12 male spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, 14-16 weeks old, were compared. 2. A flexible microdialysis probe was implanted subcutaneously in the parascapular region, and perfused with Ringer solution (flow rate: 2.0 mu L/min). After a 20 min equilibration period, NE levels were monitored over a 120 min period; then, tyramine hydrochloride (0.1 nmol/min) was perfused for 80 min. Dialysates from each 20 min collection period were analysed by HPLC with electrochemical detection for NE. 3. Basal levels of NE (adjusted for the recovery) were higher in SHR compared to WKY (1210.0 +/- 140.5 pg/mL dialysate vs 573.3 +/- 75.8 pg/mL dialysate; P < 0.001, ANOVA). In both strains tyramine perfusion increased NE concentration in dialysates; the net (i.e. baseline subtracted) NE output was lower (76.3 pg/h, s.e.m. 22.3) in SHR compared with that shown by WKY rats (201.0 pg/h, s.e.m 18.4, P < 0.01). 4. The increased basal levels of NE observed in SHR are associated with a blunted response to tyramine challenge. Since tyramine is known to cause NE release from the cytosol but not from vesicle stores, such a blunted response is consistent with an increased turnover rate of NE or with an accelerated uptake in pre-synaptic vesicles which, together with the higher basal levels, would suggest increased noradrenergic activity.

The assay of laminin fragments in serum and urine as an indicator of renal damage induced by toxins

An ELISA procedure for the assay of laminin fragments in serum and urine is described. Samples from solvent-exposed workers and diabetic patients were studied. In cohorts exposed to perchloroethylene serum and urine laminin fragments were elevated but the urinary N-acetyl-beta-D-glucosaminidase (NAG) was unaffected. The data indicate that the urinary assay may be more specific for renal damage than the serum method. Differences in the excretion of NAG and urinary laminin fragments were observed in the diabetic groups suggesting that the excretion of these two components reflects different stages of severity of the disease.

Does occupational cobalt exposure determine early renal changes?

A cohort of workers occupationally exposed to cobalt (Co) dusts was examined to assess possible subclinical renal effects attributable to Co. Cross-sectional investigations involved 26 workers with a mean age of 34.2 (S.D., 8.3), chronically-exposed (median, 3.5 years; range, 0.9-11) to Co dusts in hard-metal manufacturing factories. Thirty-five healthy control workers, with a mean age of 32.4 (S.D., 4.6) were also examined. Individual interviews were used to exclude subjects with renal or systemic diseases, intake of nephrotoxic drugs, and exposure to known nephrotoxins. Exposure levels, assessed by ambient and biological monitoring, showed an estimated exposure approaching the ACGIH-recommended TLV of 50 micrograms/m3. Immunochemical methods were used to measure urinary albumin, retinol-binding protein (RBP), beta 2-microglobulin (beta 2m), and tubular brush-border antigens. The prevalence of abnormal values for early markers of renal dysfunction was similar in Co-exposed workers and in controls. However, within the reference interval, the cumulated frequency distribution for beta 2m was shifted towards higher values in the exposed group. No relationship was detected between renal markers and either intensity or duration of exposure. In spite of a limited number of observations, these findings suggest that the kidney is not a target organ during occupational exposure to Co.

[Biological indicators and reference values]

For biological indicators of exposure, effect or susceptibility, appropriate reference values should be available for a comparative evaluation at individual or at group level. Reference values can be either measured in the same subjects before the exposure starts (internal reference), or extrapolated from an appropriately selected group (external reference). In both cases, confounding factors as well as possible sources of variability (biological and analytical), must be taken into account and controlled. Proceeding from clinical chemistry to occupational and environmental medicine, different exclusion and partition criteria in producing reference values should be adopted. Whereas clinical chemistry is aimed at discriminating people as having or not diseases, preventive medicine deals with healthy subjects to prevent effects derived from abnormal exposure to xenobiotics. To this purpose, it is mandatory that general requirements are satisfied, such as the clear definition of the reference population, the conditions under which the specimens were obtained, the adequacy of the indicator itself to provide information, provided that all laboratory results were produced by adequately standardized methods under sufficient quality control. Since we are shifting from macro to microdoses, reference values would help in discriminating natural or man-made sources of exposure.

Markers of early renal changes induced by industrial pollutants. II. Application to workers exposed to lead

The present study has been carried out in the framework of a collaborative research project on the development of new markers of nephrotoxicity. A battery of more than 20 potential indicators of renal changes has been applied to 50 workers exposed to lead (Pb) and 50 control subjects. After application of selection criteria 41 exposed and 41 control workers were eventually retained for the final statistical analysis. The average blood Pb concentration of exposed workers was 480 micrograms/l and their mean duration of exposure was 14 years. The battery of tests included parameters capable of detecting functional deficits (for example, urinary proteins of low or high molecular weight), biochemical alterations (for example, urinary eicosanoids, glycosaminoglycans, sialic acid) or cell damage (for example, urinary tubular antigens or enzymes) at different sites of the nephron or the kidney. The most outstanding effect found in workers exposed to Pb was an interference with the renal synthesis of eicosanoids, resulting in lower urinary excretion of 6-keto-PGF1 alpha and an enhanced excretion of thromboxane (TXB2). The health significance of these biochemical alterations, detectable at low exposure to Pb is unknown. As they were not associated with any sign of renal dysfunction, they may represent reversible biochemical effects or only contribute to the degradation of the renal function from the onset of clinical Pb nephropathy. The urinary excretion of some tubular antigens was also positively associated with duration of exposure to Pb. Another effect of Pb that might deserve further study is a significant increase in urinary sialic acid concentration.

Markers of early renal changes induced by industrial pollutants. III. Application to workers exposed to cadmium

Cadmium (Cd) was the third heavy metal investigated in the European collaborative research project on the development and validation of new markers of nephrotoxicity. Fifty workers exposed to Cd and 50 control workers were examined. After application of selection criteria 37 workers (mean age 43) exposed to Cd for an average of 11.3 years; and 43 age matched referents were retained for final analysis. The average concentrations of Cd in blood (Cd-B) and urine (Cd-U) of exposed workers were 5.5 micrograms Cd/l and 5.4 micrograms Cd/g creatinine respectively. By contrast with lead and mercury, Cd had a broad spectrum of effects on the kidney, producing significant alterations in amounts of almost all potential indicators of nephrotoxicity that were measured in urine--namely, low and high molecular weight proteins, kidney derived antigens or enzymes, prostanoids, and various other biochemical indices such as glycosaminoglycans and sialic acid. An increase in beta 2-microglobulin and a decrease of sialic acid concentration were found in serum. Dose-effect/response relations could be established between most of these markers and Cd-U or Cd-B. The thresholds of Cd-U associated with a significantly higher probability of change in these indicators were estimated by logistic regression analysis. Three main groups of thresholds could be identified: one around 2 micrograms Cd/g creatinine mainly associated with biochemical alterations, a second around 4 micrograms Cd/g creatinine for high molecular weight proteins and some tubular antigens or enzymes, and a third one around 10 micrograms Cd/g creatinine for low molecular weight proteins and other indicators. The recent recommendation by the American Conference of Governmental Industrial Hygienists (ACGIH) of 5 micrograms Cd/g creatinine in urine as the biological exposure limit for occupational exposure to Cd appears thus justified, although for most of the effects occurring around this threshold the link with the subsequent development of overt Cd nephropathy is not established. In that respect, the very early interference with production of some prostanoids (threshold 2 micrograms Cd/g creatinine) deserves further investigation; although this effect might contribute to protect the filtration capacity of the kidneys, it might also play a part in the toxicity of Cd on bone.

On the need of a sampling strategy in biological monitoring: the example of hexane exposure

Ambient and biological monitoring of hexane exposure were repeatedly carried out in 14 female shoe makers. Airborne hexane (Ci-H) was measured in 4-h samples collected by a diffusive method. Urinary spot samples were collected before, during (at noon), and at the end of a work shift. 2,5-Hexanedione (2,5HD) in urine collected at noon was poorly related to morning Ci-H. End-of-shift 2,5HD were also poorly related to afternoon air samples. The correlation was still relatively low when end-of-shift 2,5HD was related to 8-h TWA Ci-H (r = 0.44; P < 0.01 on a linear scale, and r = 0.58, P < 0.01 on a log-log scale). End-of-shift 2,5HD levels estimated on the basis of pre-shift values using a mathematical model were much higher (2.3 times on average) than those experimentally measured during the study period. Owing to its relatively long half-time, 2,5HD seems to be influenced not only by current exposure, but also by hexane absorbed during the day(s) preceding sampling. The lack of a sampling strategy may account not only for inconsistencies between environmental and biological data, but also for a possible misuse of biological monitoring when utilized for risk assessment. Despite sometimes poor correlations with Ci-H, 2,5HD may still be preferred to other indicators as a marker of effective internal dose. A sampling strategy should ensure that measured values are representative of the individual risk for adverse effects.

Markers of early renal changes induced by industrial pollutants. I. Application to workers exposed to mercury vapour

Several markers of renal changes have been measured in a cohort of 50 workers exposed to elemental mercury (Hg) and in 50 control workers. After application of selection criteria 44 exposed and 49 control workers were retained for the final statistical analysis. Exposed workers excreted on average 22 micrograms Hg/g creatinine and their mean duration of exposure was 11 years. Three types of renal markers were studied--namely, functional markers (creatinine and beta 2-microglobulin in serum, urinary proteins of low or high molecular weight); cytotoxicity markers (tubular antigens and enzymes in urine), and biochemical markers (eicosanoids, thromboxane, fibronectin, kallikrein, sialic acid, glycosaminoglycans in urine, red blood cell membrane negative charges). Several bloodborne indicators of polyclonal activation were also measured to test the hypothesis that an immune mechanism might be involved in the renal toxicity of elemental Hg. The main renal changes associated with exposure to Hg were indicative of tubular cytotoxicity (increased leakage of tubular antigens and enzymes in urine) and biochemical alterations (decreased urinary excretion of some eicosanoids and glycosaminoglycans and lowering of urinary pH). The concentrations of anti-DNA antibodies and total immunoglobulin E in serum were also positively associated with the concentration of Hg in urine and in blood respectively. The renal effects were mainly found in workers excreting more than 50 micrograms Hg/g creatinine, which corroborates our previous estimate of the biological threshold of Hg in urine. As these effects, however, were unrelated to the duration of exposure and not accompanied by functional changes (for example, microproteinuria), they may not necessarily represent clinically significant alterations of renal function.

Nephropathies and exposure to perchloroethylene in dry-cleaners

Even in specific risk groups, the relation between exposure to organic solvents and chronic renal diseases remains controversial. Thus, in a collaborative European study, we assessed the renal effects of occupational exposure to perchloroethylene (PCE) in dry-cleaners compared with matched controls who were simultaneously examined. Single high and low molecular weight proteins, kidney-derived antigens and enzymes, and prostanoids were measured in urine. beta 2-microglobulin, creatinine, laminin fragments, and anti-glomerular basement membrane antibodies were also measured in serum. A canonical function based on 23 such variables correctly classified 93% of individuals as either PCE-exposed or controls; with 13 markers, group membership was identified in 87% of subjects. Increased high molecular weight protein in urine was frequently (17/50 vs 1/50, p less than 0.0001) associated with tubular alterations. Changes were consistent with diffuse abnormalities along the nephron in workers exposed to low levels of PCE (median 15 parts per million). Generalised membrane disturbances might account for the increased release of laminin fragments, fibronectin, and glycosaminoglycans, for high molecular weight proteinuria, and for the increased shedding of epithelial membrane components from tubular cells with different location along the nephron (brush-border antigens and Tamm-Horsfall glycoprotein). These findings of early renal changes indicate that solvent-exposed subjects, especially dry-cleaners, need to be monitored for the possible development of chronic renal diseases.

[Lymphocyte subpopulations in workers exposed occupationally to styrene]

In a group of 32 workers occupationally exposed to styrene, the distribution of lymphocyte subsets was investigated by automated flow cytometry. The group under study consisted of 22 male and 10 female workers aged 39.7, D.S. = 10 years and employed for 6.8 years in factories manufacturing glass fibre-reinforced plastics. A control group (12 males and 7 females) recruited according to the same selection criteria was simultaneously examined. Environmental and biological monitoring was used to characterize styrene exposure. In styrene-exposed workers, phenotypic analysis of peripheral blood revealed a reduced proportion of T helper lymphocytes and a relative increase in the T suppressor subset, leading to a significant inversion of the helper/suppressor ratio (0.92) among heavily exposed workers (greater than 50 ppm, 8h-TWA) as compared to less exposed workers and controls (1.37 and 1.43 respectively). The proportion of natural killer (NK) T lymphocytes was significantly increased among styrene workers. The proportion of B lymphocytes was unchanged as compared to the control group. Dose-response relationships were clearly apparent for the observed increases in the prevalence of abnormalities: none of control subjects showed more than 2 (out of 8) abnormal values as compared to 20 and 40% of styrene workers belonging respectively to the low and high exposure group (p less than 0.007). Only a minority of controls exhibited abnormally high levels of both NK and suppressor T lymphocytes (0-5%), the corresponding figures for styrene workers being 7-10% (low exposure) and 45% (high exposure). As a whole, the findings support the hypothesis of the immunotoxicity of styrene, which could be due either to direct effects on lymphocytes or to indirect mechanisms possibly mediated by neuroendocrine changes.

Urinary excretion of brush-border antigen and plasma proteins in early stages of diabetic nephropathy

In 109 patients with insulin-dependent diabetes mellitus (IDDM), we measured the urinary excretion of albumin, the low molecular weight proteins (LMWP) retinol-binding protein (RBP) and beta 2-microglobulin (beta 2m), and brush-border antigens (BBA) revealed by monoclonal antibodies. All such markers of kidney damage and/or dysfunction were higher in diabetic patients than in 44 controls. Increased urinary levels of BBA (p = 0.0001) were associated with higher values of albumin (p = 0.0002), RBP (p = 0.0005) and, to a lesser extent, of beta 2m (p = 0.1), different combinations of values above the reference limits being observed. Some 30 and 40% of patients with and without microalbuminuria, respectively, also exhibited signs of tubulopathy. Although under certain circumstances tubular defects may give rise to small increases in albuminuria, the most likely explanation for our findings is the coexistence of glomerular and tubular damage in some patients with IDDM. Neither the prognostic value nor the pathophysiological meaning of tubular damage and/or dysfunction can be assessed by the present study, owing to its cross-sectional design. Tubular markers thus deserve further studies to clarify whether in diabetic patients they indicate a more severe or diffuse kidney impairment.

[The nephrotoxicity of ionic and nonionic contrast media in urography. An evaluation with immunoenzyme technics and monoclonal antibodies]

The nephrotoxicity of ionic and nonionic contrast media (cm) was evaluated in 52 patients undergoing pyelography. The contrast media were i.v. injected in 30'. Urine samples were collected before, 2 and 48 hours after the injection. Urinary albumin (alb) and retinol binding protein (RBP) excretion was evaluated by immunoenzymatic methods; alb and RBP were considered as indicators of glomerular permeability and of tubular reabsorption, respectively. The urinary excretion of brush-border antigen of proximal tubule (BBA) was also measured, as an indicator of microtissue damage, by a sensitive double-antibody ELISA with monoclonal antibodies. The results demonstrate ionic cm to have greater functional effects than nonionic ones, as suggested by the increased urinary excretion of both alb and RBP. However, tubular damage seemed to be more severe with nonionic agents, as suggested by BBA excretion. Although toxic damage had little significance for the patients' health, long-term effects are not to be excluded.

Endocrine effects of psychological stress associated with neurobehavioral performance testing

Twenty-four healthy subjects were submitted to a computer-based performance evaluation system. The set of tests required sustained attention, and the last test was expressly designed to cause a moderate, acute psychological stress. Compared to baseline levels, both serum ACTH and beta-endorphins were increased after psychological testing in all subjects. Serum prolactin showed a slight and statistically nonsignificant decrease compared to baseline values. These results question the belief that psychological stress stimulates prolactin secretion, whereas it suggests that serum ACTH and beta-endorphins are reliable indicators of acute psychological stress.

Brain dopamine as a target for solvent toxicity: effects of some monocyclic aromatic hydrocarbons

Adult male rabbits were exposed to toluene, xylene, styrene, ethylbenzene, vinyltoluene or were dosed with hippuric, methylhippuric, mandelic, phenylglyoxylic, and 7-methyl-mandelic acids. Styrene, vinyltoluene and ethylbenzene caused a marked depletion of striatal and tubero-infundibular dopamine. Such an effect was also caused by treatment with mandelic and phenylglyoxylic acids. These results indicate that dopamine is a target for some solvents of their metabolites, the presence of a lateral vinyl- or ethyl-chain which may be biotransformed into alpha-keto acids being crucial for the effect. Experiments in vitro suggest that dopamine condenses non-enzymatically with reactive carbonylic groups of such and other alpha-keto acids, thus becoming ineffective as neurotransmitter. This mechanism might account for the neurobehavioral and neuroendocrine changes which have been reported in workers occupationally exposed to styrene and to some solvent mixtures.

Adrenal response in the pathogenesis of arterial hypertension in workers exposed to high noise levels

Some neuroendocrine parameters known as stress indices were examined in two groups of healthy male workers in a glass factory: the first group (60 subjects) was exposed to high environmental noise levels [greater than 90 dB(A)]; the second group (52 subjects) was exposed to low noise levels [less than 78 dB(A)]. Subjects with histories of cardiovascular diseases or high arterial pressure were excluded from the study. In both groups serum catecholamines and cortisol, and urinary vanilmandelic and homovanillic acids were evaluated at the beginning and middle of morning and afternoon work-shifts, by high performance liquid chromatography with electrochemical detection. Norepinephrine, epinephrine and vanilmandelic acid were significantly increased (P less than 0.01) during work-shifts in the group exposed to 90 dB(A), compared with baseline levels and also with catecholamine levels in the group exposed to 78 dB(A). Serum dopamine, cortisol and homovanillic acid showed no significant differences. The increased stimulation of the sympatho-adrenal system in response to high and prolonged noise exposure might lead to an abnormal response of the cardiovascular system with increasing arterial pressure values.

A cross-sectional survey of kidney function in refinery employees

We examined sensitive biochemical and immunological markers of kidney function and damage in 53 male oil refinery workers exposed to hydrocarbons and compared their results with those of a control group of 61 age-matched nonexposed males. The mean duration of employment of exposed males was 11 years. The current levels of exposure to a variety of aliphatic and aromatic hydrocarbons, as determined by personal monitoring, were well below the current threshold limit values. No difference was found in the urinary tubular parameters beta-N-acetyl-D-glucosaminidase, beta 2-microglobulin (beta 2-m) and retinol-binding protein. Similar serum beta 2-m levels indicated no impairment of the glomerular filtration rate in the exposed workers. The levels of circulating immune complexes were also identical in both groups. The mean albuminuria was slightly higher (p less than .005) in the exposed group in a quantitative assay but was not dipstick-detectable. The mean urinary excretion of a renal antigen was also higher (p less than .05) in the exposed group and correlated with the excretion of albumin. Finally, slightly higher titers of anti-laminin antibodies were found in five exposed employees, but this was not accompanied by an increased albuminuria. We conclude that chronic low-level hydrocarbon exposure in these refinery workers does not lead to clinically significant renal abnormalities. Nevertheless, some findings are consistent with the possible role of hydrocarbon exposure in the induction of renal disturbances.

Effects of some monocyclic aromatic solvents and their metabolites on brain dopamine in rabbits

Adult male rabbits were exposed to high concentrations (750 ppm, 12 hours daily for 7 days) of toluene, xylenes, styrene, ethylbenzene, vinyltoluene (3-methylstyrene), and 7-methyl-styrene vapours or were dosed with 4 mM/kg/day i.p. of hippuric, methylhippuric, mandelic, phenylglyoxylic, and 7-methyl-mandelic acids. Styrene, vinyltoluene and ethylbenzene caused a marked depletion of striatal and tuberoinfundibular dopamine. Such an effect was also caused by treatment with phenylglyoxylic and mandelic acids. Dopamine depletion was associated with an increase in homovanillic acid concentration in the same regions. These results indicate that dopamine metabolism is a target for the neurotoxic effects of some monocyclic aromatic hydrocarbons and their metabolites, a lateral vinyl- or ethyl-chain being crucial for the structure/activity relationship of such compounds.

Urinary excretion of brush-border antigen revealed by monoclonal antibody: early indicator of toxic nephropathy

Mouse monoclonal antibodies against brush-border antigens of the proximal tubule of human kidney were produced by the hybridisation technique. The urinary excretion of a brush-border protein with an apparent molecular weight of 50 000 (BB-50) was measured by a sandwich enzyme-linked immunosorbent assay with a mouse IgG1 against BB-50 and a polyclonal rabbit antiserum against human kidney as coating and second antibodies. The urinary excretion of BB-50 was fifty times higher in patients treated with cisplatin than in a matched control group and twice as high in workers occupationally exposed to water-soluble chromium(VI) compounds as in their matched controls. These findings suggest that the urinary excretion of kidney antigens revealed by monoclonal antibodies is a very sensitive and specific test for the assessment of toxic nephropathies.

Styrene metabolism and striatal dopamine depletion in rabbits

The striatal concentration of dopamine (DA), norepinephrine (NE), and homovanillic acid (HVA) was assessed in adult male rabbits exposed to styrene vapours or dosed with mandelic acid (MA), phenylglyoxylic acid (PGA) and phenylglycine (PG). Styrene exposure produced a marked and dose-dependent decrease in striatal DA, concomitant with a consistent increase in HVA. The same effects were caused by i.p. administration of PGA and PG, but not of MA. The increased catabolism of DA was concomitant with a normal turnover time after inhibition of tyrosine hydroxylase by the administration of methyl-p-tyrosine. The amination of PGA to PG with a subsequent competition of the latter with DA for the vesicular storage capacity is suggested as the possible mechanism for styrene-induced brain dysfunction.

n-Hexane metabolism in occupationally exposed workers

Lung uptake and excretion of n-hexane were studied in ten workers in a shoe factory. Simultaneous samples of inhaled and alveolar air were collected with the aid of a Rhan-Otis valve, personal samplers, and charcoal tubes. Alveolar excretion was monitored during a six hour postexposure period. Uptake was calculated from lung ventilation, the retention coefficient, and environmental concentrations. The amount of exhaled n-hexane was calculated from the decay curve. According to the experimental data, alveolar retention was about 25% of the inhaled n-hexane, corresponding to a lung uptake of about 17%. The postexposure alveolar excretion was about 10% of the total uptake. The main metabolites of n-hexane were identified and measured by capillary GC/MS in spot urine samples collected before, at the end, and 15 hours after the same working shift. Urinary concentrations were low, though related to n-hexane in the air. 2,5-Hexanedione in the end of shift samples gave the best estimate of overall exposure. About 3 mg/g creatinine of 2,5-hexanedione would correspond to about 50 ppm of n-hexane in the air (mean daily exposure).

Regional alterations of brain catecholamines by styrene exposure in rabbits

The regional distribution of dopamine, norepinephrine and homovanillic acid was assessed in adult male rabbits exposed to styrene vapours. The turnover of dopamine and norepinephrine was also measured in several brain regions by the decay in endogenous catecholamines after inhibition of tyrosine hydroxylase by alpha-methyl-p-tyrosine. Styrene exposure produced a marked and dose-dependent decrease in striatal and tuberoinfundibular dopamine, associated with a consistent increase in homovanillic acid content in the same regions. Norepinephrine levels were unaffected by styrene exposure. The observed increase in catabolism of dopamine cannot be explained by the turnover time, which was not significantly different in the exposed as compared to the control rabbits. Competition of a styrene metabolite with dopamine for the vesicular storage capacity or a selective destruction of dopaminergic terminals are suggested as the possible mechanisms for styrene neurotoxicity.

Neuroendocrine effects of styrene on occupationally exposed workers

The serum levels of prolactin (PRL), human growth hormone (HGH), thyroid-stimulating hormone (TSH), and the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured in 30 females exposed to about 130 (range 65-300) ppm of styrene in the air and in 30 age-matched referents to show whether styrene exposure influences the dopaminergic tuberoinfundibular system (TIDA). The exposed subjects' serum levels of PRL were more than double the reference values and were significantly related to the urinary excretion of styrene metabolites, ie, to the sum of mandelic acid (MA) and phenylglyoxylic acid (PGA) in the "next-morning" urine spot sample. Such a relationship still proved to be statistically significant after the removal of the effects of age and duration of exposure with the method of partial correlation. The serum concentrations of HGH in the exposed workers were also higher than in the reference group. Though within the reference levels, the TSH values of the exposed subjects were significantly related to the urinary excretion of MA and PGA. These results are consistent with the dose-dependent depletion in tuberoinfundibular dopamine after experimental styrene exposure of rabbits.