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.