A cross-sectional survey of kidney function in refinery employees

Some Biochemical and Hematological Parameters among Petrol Station Attendants: A Comparative Study

Objective. To describe selected biochemical and hematological parameters (blood picture, liver enzymes, and kidney functions) in petrol station attendants in Mansoura city. Methods. This is a comparative cross-sectional study. The exposed group included 102 petrol station attendants. They were compared to a matched group of healthy 102 male service and office workers at the Faculty of Medicine, Mansoura University. The results of blood picture, liver enzymes, and kidney functions were compared between both groups. Results. Mean Red Blood Cells (RBCs) count, hemoglobin level, and Hematocrit (HCT) level were significantly lower in petrol station attendants than the comparison group. All other blood picture parameters showed nonsignificant difference between both groups. Liver enzymes, renal functions, serum albumin, and total protein showed statistically nonsignificant difference between both groups except for alanine aminotransferase (ALT) which was significantly higher in petrol station attendants. Conclusions. Some laboratory parameters among petrol station attendants showed changes that could be attributed to workplace exposure and should be given attention at preemployment and periodic medical examination.

Current understandings and perspectives on non-cancer health effects of benzene: a global concern

OBJECTIVE

Benzene, as a volatile organic compound, is known as one of the main air pollutants in the environment. The aim of this review is to summarize all available evidences on non-cancerous health effects of benzene providing an overview of possible association of exposure to benzene with human chronic diseases, specially, in those regions of the world where benzene concentration is being poorly monitored.

METHODOLOGY

A bibliographic search of scientific databases including PubMed, Google Scholar, and Scirus was conducted with key words of "benzene toxic health effects", "environmental volatile organic compounds", "diabetes mellitus and environmental pollutants", "breast cancer and environmental pollution", "prevalence of lung cancer", and "diabetes prevalence". More than 300 peer reviewed papers were examined. Experimental and epidemiologic studies reporting health effects of benzene and volatile organic compounds were included in the study.

RESULTS

Epidemiologic and experimental studies suggest that benzene exposure can lead to numerous non-cancerous health effects associated with functional aberration of vital systems in the body like reproductive, immune, nervous, endocrine, cardiovascular, and respiratory.

CONCLUSION

Chronic diseases have become a health burden of global dimension with special emphasis in regions with poor monitoring over contents of benzene in petrochemicals. Benzene is a well known carcinogen of blood and its components, but the concern of benzene exposure is more than carcinogenicity of blood components and should be evaluated in both epidemiologic and experimental studies. Aspect of interactions and mechanism of toxicity in relation to human general health problems especially endocrine disturbances with particular reference to diabetes, breast and lung cancers should be followed up.

New insight into solvent-related end-stage renal disease: occupations, products and types of solvents at risk

OBJECTIVES

It has been shown that all-solvent exposure is associated with the progression of primary glomerulonephritis to end-stage renal disease (ESRD), but little is known about the type of solvents that are high risk. The aim of this study was to investigate the role of solvents by occupation, product and type.

METHODS

Using a retrospective cohort design, the authors studied 269 patients with non-end-stage and biopsy-proven primary glomerulonephritis diagnosed between 1994 and 2001 in Paris and its suburbs. Two industrial hygienists evaluated patients' exposures from lifetime occupational histories collected by interview from 2002-4, and using a list of the 30 most common solvents. The studied outcome was ESRD, defined as glomerular filtration rate <15 ml/mn/1.73 m(2) or dialysis. It was recorded during a mean follow-up of five years. Cox models were used to estimate adjusted hazard ratios (HR) of ESRD related to exposures.

RESULTS

Eighteen per cent of the patients had ever been exposed to solvents. Those with the highest risk of progression to ESRD were exposed machinery fitters and machine assemblers (HR 4.7, 95% CI 1.2 to 17.4) and plumbers/welders (HR 4.2, 95% CI 1.3 to 13.6), as compared to never exposed patients, as well as those who ever handled printing inks and petroleum products (HR 12.6 (95% CI 1.7 to 94.9) and 3.2 (95% CI 1.4 to 7.2), respectively). Among solvents, the highest risks were found for: toluene/xylene (HR 5.1, 95% CI 1.8 to 14.8), gasoline, fuel and gas-oil (HR 8.6, 95% CI 2.7 to 27.4), and ketones (HR 13.3, 95% CI 1.4 to 123.5).

CONCLUSION

This study highlights the potential nephrotoxicity of several solvents. Intervention to promote screening for proteinuria in exposed workers may prevent the progression of glomerulonephritis to ESRD.

Nephrotoxicity of organic solvents: biomarkers for early detection

OBJECTIVES

Evidence for a relationship between chronic kidney diseases or progression of already existing diseases (glomerulonephritides) and occupational solvent exposure has been found in case reports, in case-control studies and also in cross-sectional studies. An analysis of the available literature was performed with respect to markers measured in cross-sectional studies that might be useful for an early detection of solvent-induced effects on the kidney.

METHODS

The relevant cross-sectional studies were evaluated and the following markers were analyzed with respect to their suitability as biomarker for renal damage: total protein, albumin, transferrin, IgG, beta(2)-microglobulin, retinol-binding protein, N-acetyl-beta-D: -glucosaminidase, alanine aminopeptidase, beta-galactosidase, beta-glucuronidase, leucin aminopeptidase, alkaline phosphatase, lysozyme, Tamm-Horsfall protein and laminin fragments in urine as well as E-selectin, laminin and anti-laminin antibodies and anti-glomerular basement membrane antibodies in serum.

RESULTS

An increased albumin excretion was observed more frequently in groups of workers exposed to various solvents (like toluene, styrene, aliphatic/aromatic hydrocarbon mixtures, tetrachloroethene, mixtures of chlorinated hydrocarbons) than in controls. No clear pattern emerged for the other markers.

CONCLUSIONS

The determination of albumin excretion in the urine appears to be a useful parameter for monitoring solvent-exposed workers.

Land contamination and urinary abnormalities: cause for concern?

AIMS

To determine the prevalence of proteinuira and enzymuria among a cohort of subjects exposed to hexachlorobutadiene (HCBD) in their homes and to determine whether there was a change in observed effects when exposure ceased.

METHODS

Residents underwent a health check, which included a panel of urinary markers of both glomerular and tubular origin, within two months of cessation of long term exposure to HCBD and again at least 10 months after exposure ceased. Analysis of the results was performed to determine if there was any early evidence of renal effects, and to ascertain whether changes in these parameters occurred after exposure to HCBD ceased.

RESULTS

Tubular proteinuria and enzymuria were increased in the initial health check and significantly decreased after the residents had left their homes for about 10 months. As the early renal tubular markers improved when exposure ceased it is anticipated that the long term nephrotoxic risk will be minimal, but the carcinogenic risk remains unknown.

CONCLUSIONS

Results show there was a renal effect which improved when subjects left their homes. This suggests there was a local environmental factor responsible for the observations. This is consistent with the predicted toxicological effects of HCBD from animal studies.

Working condition-related improvement in genotoxicological parameters of Hungarian road pavers

Multiple-endpoint follow-up genotoxicology monitoring was performed in a group of 22 Hungarian road pavers between 1996 and 1999. The studied endpoints were the determination of structural and numeric chromosome aberration (CA), sister chromatid exchange (SCE), high-frequency SCE and HPRT mutation frequencies, and ultraviolet (UV)-light-induced unscheduled DNA synthesis in peripheral blood lymphocytes (PBLs). The workers (8 hand pavers and 14 finishers, mean age 37 yr) used tar-free asphalt. The results were compared with those of 6 work-site controls (35 yr), 101 historical controls (38 yr), and 87 industrial controls (38 yr). The most marked changes were found in the CA frequencies. In the control, the mean CA frequency was 1.6%. In the first study, increased CA frequencies were found in the donors that either had been exposed to hot asphalt fumes or had cleaned the equipment with crude oil. The mean CA frequency of the 14 finishers working in closed cabins was 3.67% in 1996. The increased CA frequency was attributed to the high level of hot asphalt fumes due to insufficient ventilation. By 1999 the mean CA frequency decreased to 1.23%. For the 8 hand pavers working in open air the mean CA frequency was 3.6% in 1996. The obtained data suggested that the increase in CA frequencies was due to the use of petroleum and crude oil; therefore, these substances were replaced with harmless detergents. By 1999 the mean CA frequency decreased to 1%. In finishers the mean CA frequency returned to the control level 1 yr later (1999) than in the case of hand pavers. The chromosome-type aberrations remained predominant during the follow-up. The individual variations observed were attributed to smoking and inadequate personal protection. The obtained results suggest that the use of tar-free asphalt and harmless detergents with adequate personal protection does not increase the frequencies of the genotoxicological parameters compared to controls. Consequently, an improvement in working conditions can prevent further exposures and thus decrease the cancer risk of road pavers.

Biomarkers in occupational volatile organic chemical exposure

Evidence exists that in certain groups of workers exposed to volatile organic chemicals, there is subclinical renal damage and dysfunction. Also, there is activation of biological mechanisms that are suggested links between volatile organic chemical exposure and renal disease. Notably, the workers studied are employed in factories where exposures are considered controlled, with on-site professional health and safety management. Recent studies continue to indicate an increased risk of renal disease in those exposed to volatile organic chemicals.

Exposure to hydrocarbons and renal disease: an experimental animal model

The association between hydrocarbon exposure and chronic glomerulonephritis is still a controversial scientific issue. Recent epidemiological evidence suggests a role of exposure to hydrocarbons in the progression of glomerulonephritis towards chronic renal failure. The present experimental study on rats has been designed to assess the possible role of styrene in the progression of adriamycin (ADR) nephrosis, a well known model of renal fibrosis following nephrotic syndrome induced by ADR. Female Sprague-Dawley rats were exposed to styrene, 300 ppm, 6 h/day, 5 days/week for 12 weeks (group 1); treated with ADR, 2 mg/Kg, i.v., twice on day 1 and day 15 of the study (group 2); Additional groups of animals received both the styrene and ADR treatments (group 3) or served as controls (group 4). The urinary excretion of total and single proteins (albumin, Retinol-Binding Protein (RBP), Clara Cell 16 Kd protein (CC16), fibronectin) was measured monthly, whereas histopathology and determinations requiring blood sampling were carried out at the end of the experiment. A progressive increase in total proteinuria, falling in the nephrotic range already by the 6th week was observed in ADR-treated groups. Styrene exposure caused up to a 3- to 5-fold increase as compared to controls. Co-exposure to ADR and styrene also resulted in a proteinuria much greater than that caused by ADR alone. The interactive effect of styrene and ADR was statistically significant for albuminuria and urinary fibronectin. A similar response was observed for glomerular filtration rate at the end of the experiment, styrene-exposed animals showing hyperfiltration as compared to their respective control group. At the end of the experiment, histopathological scoring for interstitial infiltration and fibrosis was also significantly higher in styrene-treated animals as compared to their respective control groups. In ADR-treated rats, low molecular weight proteinuria (l.m.w.p.) was only slightly affected, suggesting minimal tubular dysfunction associated with extensive tubular atrophy. However, styrene-exposed animals showed l.m.w.p. higher than their respective controls. In summary, in this animal model we were able to confirm both styrene-induced microproteinuria, mainly albuminuria and minor increases in l.m.w.p., observed among occupationally exposed workers and the role of hydrocarbon exposure as a factor accelerating the progression of renal disease suggested by epidemiological investigations in patients suffering from chronic renal disease. Whereas in rats exposed to styrene only, microproteinuria was stable over time and minor histopathological changes were noted at the end of the experiment, evidence of a role of solvent exposure in the progression of ADR nephropathy was obtained in terms of both renal dysfunction and interstitial fibrosis. The mechanistic basis of styrene-ADR interaction is unclear. However, experimental evidence is consistent with epidemiological findings suggesting the need to avoid solvent exposure in patients suffering from renal diseases.

Occupational hydrocarbon exposure and nephrotoxicity: a cohort study and literature review

Hydrocarbon exposure has been shown to play an important role in the development of renal dysfunction in several occupational settings. In this study, renal screening was performed in a group of paint sprayers with exposure to hydrocarbon-based paints, recruited from a car manufacturing plant where personal protective equipment was widely used. The hydrocarbon exposure scores and various markers of renal injury were compared between these subjects and a group of paint sprayers from a previous study who did not use personal protective equipment regularly. Cumulative hydrocarbon exposure scores were calculated from a validated questionnaire. Serum creatinine, urinary total protein, albumin, transferrin, retinol-binding protein, and N-acetylglucosaminidase were evaluated, Both groups experienced heavy hydrocarbon exposure but sprayers who regularly used personal protective equipment had significantly reduced exposure scores due to improved skin and respiratory protection. A significant number of sprayers from both groups had elevated levels of serum creatinine. Interestingly, urinary N-acetylglucosaminidase activity, a marker of proximal tubular damage, was abnormal in a significant proportion of sprayers in the unprotected group but normal in those with improved protection. Our results are in keeping with the hypothesis that hydrocarbon exposure through paint spraying may result in active proximal tubular damage which may be reduced by improvement of protection at the worksite. However, renal impairment independent of tubular injury may result from chronic paint exposure, even with improved protection.

Hydrocarbon exposure and chronic renal disease

The study objective was to investigate further the potential role of long-term exposure to hydrocarbons (HCs) in the development of idiopathic chronic glomerulopathy (ICG) using a more refined measurement of HC exposure. A total of 321 pairs of cases and controls, matched by age, gender, and geographical area, were assembled. A detailed questionnaire was blindly administered to cases and controls to collect information on occupational and medical history and sociodemographic data. By integrating quantified measurements of HC exposure from a variety of sources with each subject's occupational history, a lifetime HC exposure score could be estimated and expressed in parts per million (ppm). Cases had an hydrocarbon exposure mean score of 165 ppm (median 48 ppm) as compared to 162 ppm (median 43 ppm) for controls (P = 0.757). When using hydrocarbon exposure as a dichotomous variable with a cutoff point at 100 ppm, cases had a higher proportion of exposed than controls, but the difference was not statistically significant at the 0.05 level, even after controlling for possible confounders through logistic regression. Subgroup analyses showed mixed results. In most subgroups differences between cases and controls tended to become significant when hydrocarbon was used as a dichotomous variable. Results from this study do not sufficiently support the hypothesized association of HC exposure and ICG in general. Subgroup analyses need further investigations. Efforts to generate accurate estimates of lifetime HC exposure should be emphasized for future investigations.

Increased albumin excretion in industrial workers due to shift work rather than to prolonged exposure to low concentrations of chlorinated hydrocarbons

OBJECTIVES

It has been reported that groups of workers in petrochemical industries who have been exposed to low concentrations of chemicals for prolonged periods have an increased urinary albumin excretion compared with unexposed controls. This increase, however, seemed to be unrelated to the extent, duration, and type of exposure. The aim of the present study was to investigate the suggestion that the small increase in albumin excretion might be due to differences in physical workload between the exposed and control groups or to the fact that the exposed workers are shift workers whereas the controls are employed on day duty.

METHODS

To elucidate the effect of shift work, again a series of renal and hepatic variables were studied in organochlorine workers but now with two different control groups. One control group comprised shift workers and the other only workers on day duty. The exposed and both control groups had roughly equal physical workloads, although one control group comprised shift workers and the other workers who work only during day time.

RESULTS

There were no significant changes in the results of the liver tests between the exposed group and either of the control groups, nor between the two control groups. No significant differences for any renal test were found between the exposed workers and control shift workers, but albumin was significantly lower in the control day workers than in the exposed workers and control shift workers.

CONCLUSIONS

The results suggest that the previously reported small increase in albuminuria in industrial workers is due to alterations in circadian rhythms due to the shift work system rather than to prolonged exposure to low concentrations of potentially nephrotoxic chemicals.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.

Occupational factors and renal disease

The male-to-female ratio of patients requiring dialysis treatment commonly approaches 2:1. It is proposed that environmental factors, particularly occupational exposure to hydrocarbons, may account for the excess number of male patients. The term "hydrocarbon" refers to the aliphatic, alicyclic, aromatic, and halogenated hydrocarbons (carbon tetrachloride, chloroform); glycols (ethylene glycol, diethylene glycol, dioxane, glycerol); and organic solvents. Hydrocarbons commonly find use as solvents in industrial manufacturing practices because of their lipid solubility. Hydrocarbons have long been known to be neurotoxicants, affecting both peripheral and central nervous systems. Although benzene and its derivative have a known association with uroepithelial tumors, there is now a considerable body of evidence suggesting a possible role for hydrocarbon exposure in the development of non-neoplastic renal diseases. This article presents an epidemiological case for such an association and critically reviews the literature.

Effects of exposure to low concentrations of chlorinated hydrocarbons on the kidney and liver of industrial workers

An assessment has been made of biochemical alterations in renal and hepatic functions of 73 male operators employed for an average of 8.2 years (range 0.5-23 years) in a chemical plant producing chlorinated hydrocarbons. Exposure to allyl chloride (AC), 1,3-dichloropropene (DCP), epichlorohydrin (ECH), and hexachlorocyclopentadiene (HEX) has regularly been determined by personal air monitoring since 1980. Although exposures to DCP and ECH were well below currently accepted maximum allowable concentrations (MACs), relatively high exposures to AC and HEX, occasionally exceeding the MAC, have been measured. The results of the kidney and liver function tests were compared with those of a control group comprising 35 men employed at the materials division and not occupationally exposed to chemicals. Biochemical alterations of liver function were assessed by determination in serum of alanine and aspartate aminotransferases (ALAT, ASAT), alkaline phosphatase (AP), total bilirubin (BIL), gamma-glutamyltranspeptidase (GGT), lactate dehydrogenase (LDH), and total bile acids (SBA). No differences between the exposed group and the control group were found. Nor were differences found in biochemical tests for renal tubular damage (urinary alanine aminopeptidase (AAP) and N-acetyl-beta-D-glucosaminidase (NAG) and renal tubular function (urinary retinol binding protein (RBP). Total urinary protein and albumin excretion were measured to assess the integrity of the glomerulus. Urinary total protein did not differ between the groups, but urinary albumin, although within normal limits in both groups, was significantly higher (p < 0.02) in the exposed group. This difference in urinary albumin could not simply be explained by exposure to chlorinated hydrocarbons because albumin concentrations did not correlate with the duration of employment. It is concluded that long term exposure to concentrations of AC, DCP, ECH, or HEX below or near the current limit threshold value does not lead to clinically significant effects on kidney and liver.

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.

Urinary excretion of proteins and enzymes in workers exposed to hydrocarbons in a shoe factory

A cross-sectional study was conducted to determine whether exposure to hydrocarbons in a shoe factory may produce renal effects that can be detected by determination of the urinary excretion of proteins and enzymes. The study population included 59 women who had been exposed to petroleum naphtha and toluene and 24 age-matched control women. The time-weighted average exposure to petroleum naphtha, toluene and ethylacetate was 1,619,81 and 160 mg/m3, respectively. The integrity of the renal structures or functions was assessed by measuring the urinary excretion of total protein, beta 2-microglobulin, retinol-binding protein, albumin, transferrin, lysozyme, lactate dehydrogenase and beta-N-acetylglucosaminidase (NAG). The only parameter that was significantly influenced by hydrocarbon exposure was the urinary activity of beta-N-acetylglucosaminidase. Although the health significance of this renal change, which was not accompanied by changes in the urinary excretion of low- or high-molecular-weight proteins, is unclear, the results of the present study are in agreement with our previous observations suggesting that long-term moderate exposure to solvents does not entail a significant risk for the development of nephrotoxicity.

Proteinuria: changes and mechanisms in toxic nephropathies

During the last few decades, considerable progress has been made in the understanding of the pathophysiological mechanisms of proteinuria. A great variety of hemodynamic or biochemical mechanisms acting at different sites of the nephron have been shown to alter the renal handling and the urinary excretion of proteins. The finding which perhaps has had most practical implications is that the pattern of protein excretion quantitatively and qualitatively varies with the site and severity of renal damage. This has led to the development of a large array of methods for the identification and quantitation of specific urinary proteins. These methods have been most extensively used by toxicologists in experimental, epidemiological, or clinical studies on potentially nephrotoxic chemicals (e.g., drugs, heavy metals, solvents, etc.). The present review summarizes the current state of knowledge on the mechanisms of proteinuria and the use of urinary proteins as indicators of nephrotoxicity.

Toxicology update isoparaffinic hydrocarbons: a summary of physical properties, toxicity studies and human exposure data

The Isoparaffins covered in this manuscript are branched aliphatic hydrocarbons with a carbon skeleton length ranging from approximately C10 to C15. They are used in the manufacture of liquid imaging toners, paint formulations, charcoal lighter fluid, furniture polishes and floor clearners. Potential exposure exists in the petroleum, printing and paint industries. Isoparaffins have a very low order of acute toxicity, being practically non-toxic by oral, dermal and inhalation routes. However, aspiration of liquid isoparaffins into the lungs during oral ingestion could result in severe pulmonary injury. Dermally, isoparaffins have produced slight to moderate irritation in animals and humans under occluded patch conditions where evaporation cannot freely occur. However, they are not irritating in non-occluded tests, which are a more realistic simulation of human exposure. They have not been found to be sensitizers in guinea pig or human patch testing. However, occasional rare idiosyncratic sensitization reactions in humans have been reported. Instillation of isoparaffins into rabbit eyes produces only slight irritation. Several studies have evaluated sensory irritation in laboratory animals or odor or sensory response in humans. When evaluated by a standard procedure to assess upper airway irritation, isoparaffins did not produce sensory irritation in mice exposed to up to 400 ppm isoparaffin in air. Human volunteers were exposed for six hours to 100 ppm isoparaffin. The subjects were given a self-administered questionnaire to evaluate symptoms, which included dryness of the mucous membranes, loss of appetite, nausea, vomiting, diarrhea, fatigue, headache, dizziness, feeling of inebriation, visual disturbances, tremor, muscular weakness, impairment of coordination or paresthesia. No symptoms associated with solvent exposure were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary levels of proteins and metabolites in workers exposed to toluene. A cross-sectional study

We measured urinary excretion of albumin and retinol-binding proteins to investigate the occurrence of early renal dysfunction in 45 paint workers exposed principally to toluene, and in the same number of unexposed control subjects matched individually for sex and age. Two biological indicators of personal toluene absorption, namely urine hippuric acid and o-cresol, were also measured in the exposed subjects. A significantly higher level and increased prevalence of elevated retinol-binding protein in the urine of exposed workers was found, whereas no significant difference in urinary albumin concentration was seen between the two groups. Urinary concentrations of retinol-binding protein was correlated (r = 0.399, P less than 0.006) with that of o-cresol, but not with hippuric acid or employment duration. The results suggest a dose-dependent early tubular effect due to toluene exposure that might be useful for monitoring individuals exposed to toluene at work.

Epidemiological application of early markers of nephrotoxicity

This paper is a review of epidemiological studies in which sensitive markers of nephrotoxicity have been used to detect the early effects of chemicals on the kidney. Most of the studies are cross-sectional, and their objective was either to identify potentially nephrotoxic chemicals (organic solvents, heavy metals) in the working or general environment or to establish dose-response/effect relationships from which safe exposure levels can be defined (e.g., for cadmium and mercury vapour). A few longitudinal studies were conducted to determine the persistence of renal disturbances and to get information on their predictive value (e.g., microproteinuria in cadmium workers). Nephrotoxicity tests, which have proved to be the most useful in these epidemiological studies, rely on the determination of specific urinary proteins which, according to their size, reflect the functional integrity of the proximal tubule (e.g., retinol-binding protein or beta 2-microglobulin) or the glomerulus (e.g., albumin, immunoglobulin G). An increased urinary excretion of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase has been reported in several studies (e.g., in lead-exposed workers), but the pathological significance of this finding remains to be clarified, particularly when it is not associated with changes in the urinary excretion of specific proteins. Further work is needed to assess the usefulness of tests introduced more recently such as the assay of renal antigens in urine and the use of red-blood-cell membrane negative charges as an index of the glomerular polyanion. With the exception of microproteinuria observed in chronic cadmium poisoning, no epidemiological data are available on the prognostic value of subclinical renal effects caused by nephrotoxic chemicals.

Detection of renal diseases in humans: developing markers and methods

This review covers the tests currently available or being developed for early detection of renal damage and dysfunction induced by exogenous chemicals. Relevant markers are discussed with regard to their application and their level of validation. Some of these tests are being used routinely within health surveillance programmes of individuals exposed to known nephrotoxic agents. More sensitive tests can be applied in epidemiological surveillance programmes aimed at the identification and removal of relevant risk factors. The earliest changes might have little clinical significance, although new perspectives may be opened by various markers and approaches that are being developed.

Preclinical detection of nephrotoxicity: description of the tests and appraisal of their health significance

The prevention of renal diseases induced by chemicals requires the use of tests with which adverse renal effects can be detected at a stage when removal from exposure to the offending agent(s) may lead to complete recovery or may at least prevent an accelerated decline in renal function. The screening tests used in clinical medicine for assessing the functional integrity of the kidney are not sufficiently sensitive to attain this objective. In this review, we describe the tests currently available for detecting incipient renal damage and attempt to assess their health significance. A minimal battery of tests is recommended for the detection of groups in industry or in the general population who are at risk. If an increased prevalence of abnormal values for these parameters is found repeatedly in a population, efforts should be made to identify the causal agent(s) and, if possible, to reduce the exposure. Follow-up examinations of subjects identified in this way are also indicated, in order to define the predictive value of the detected changes better.

Early detection of the nephrotoxic effects of industrial chemicals: state of the art and future prospects

This paper discusses several tests that may permit the early detection of renal changes induced by long-term exposure to nephrotoxic industrial chemicals and may possibly serve as advance warning of pending renal damage. Some tests mainly attempt to assess the integrity of the glomerulus: high molecular weight proteinuria, glomerular basement membrane (GBM) antigens in blood and in urine, circulating anti-GBM antibodies, glomerular filtration rate after an acute oral load of proteins, and estimation of membrane negative charges (ie, glomerular polyanion). Others mainly attempt to identify functional and/or morphological changes at the tubular level: low molecular weight proteinuria, aminoaciduria, glucosuria, hyperphosphaturia, hypercalciuria, enzymuria, tubular antigen excretion, kallikrein, and prostaglandin excretion. Some of these tests are already routinely used, although controversy may still persist with regard to their clinical significance. Recently, new tests have been developed that may open new perspectives for assessing the significance of the early renal changes induced by chemicals.