Kidney function in stainless steel welders

[Complications of metal-on-metal tribological pairing]

BACKGROUND

Metal-on-metal (MoM) tribological pairing results in less volumetric abrasion than pairing with the conventionally used polyethylene and is associated with a lower risk of material failure compared to other hard-hard pairings. An increased frequency of problem cases in recent years has led to a great increase in uncertainty. Against this background in this article the current aspects of epidemiology, etiology, diagnostics and treatment of complications in MoM hip joint endoprostheses will be discussed.

EPIDEMIOLOGY AND ETIOLOGY

Based on the results from national endoprosthesis registers and selected clinical studies an evaluation of the rate of local complications from MoM tribological pairings was undertaken. A differentiation was made between MoM pairings in pedicled small head prostheses (≤ 32 mm), large head (> 32 mm) and surface replacement (OFE) endoprostheses. Each year MoM endoprostheses release on average 10(12)-10(14) cobalt (Co) and chromium (Cr) nanoparticles per patient. This release of metal ions and particles can lead to a variety of tissue reactions.

DIAGNOSTICS

A differentiation must be made between regular routine diagnostics within the framework of implant follow-up screening and specific investigations due to the occurrence of complaints. The diagnostics for patients treated with MoM hip endoprostheses consists of a standardized step-wise approach considering possible differential diagnoses and the utilization of modern laboratory chemical and radiological methods. When problems occur, a differentiation should preferentially be made between complaints not caused by metal and mechanical problems (e.g. prosthesis loosening and impingement) and symptoms due to periprosthetic infections.

THERAPY OF COMPLICATIONS

The normal standards for hip endoprosthetics are also valid for periprosthetic infections, fractures and other general complications. Specific measures are, however, necessary for complications due to metal-specific risks.

Chromium

Chromium occurs primarily in the trivalent state (III), which is the most stable form, or in the hexavalent state (VI), which is a strong oxidizing agent. Elemental chromium (0) does not occur naturally on earth. Trivalent chromium (III) is an essential trace metal necessary for the formation of glucose tolerance factor and for the metabolism of insulin. Commercial applications of chromium compounds include tanning (III), corrosion inhibition, plating, glassware-cleaning solutions, wood preservatives (VI), manufacture of safety matches, metal finishing (VI), and the production of pigments (III, VI). Hexavalent chromium (VI) contaminated local soil when chromium waste slag was part of the fill material present in residential, public, and industrial areas. In some urban areas, about two-thirds of the chromium in air results from the emission of hexavalent chromium from fossil fuel combustion and steel production. The remaining chromium in air is the trivalent form. The residence time of chromium in air is < 10 days, depending on the particle size. Trivalent compounds generally have low toxicity and the gastrointestinal tract poorly absorbs these compounds. Hexavalent chromium is a skin and mucous membrane irritant and some of these hexavalent compounds are strong corrosive agents. Hexavalent chromium compounds also produce an allergic contact dermatitis characterized by eczema. Sensitivity to trivalent compounds is much less frequent, but some workers may react to high concentrations of these compounds. Hexavalent chromium is recognized by the International Agency for Research on Cancer and by the US Toxicology Program as a pulmonary carcinogen. The increased risk of lung cancer occurs primarily in workers exposed to hexavalent chromium dust during the refining of chromite ore and the production of chromate pigments. Although individual studies suggest the possibility of an excess incidence of cancer at sites outside the lung, the results from these studies are inconsistent.

Urinary excretion of proteins among metal welders

Joining of metals by welding confer an exposure of dust particulates containing several toxic substances. Chromium, nickel and manganese is absorbed in the lungs and may adversely affect the renal function. We compared biological markers of glomerular filtration (Kampmann clearance) and tubular function (post-shift urine spot sample concentration of respectively albumin, immunoglobulin G, transferrin, orosomucoid and beta 2-microglobulin) among 102 ever-welders and 33 never-welders (mostly electricians). The welders were subdivided into groups of stainless steel welders (n = 35), mild steel welders (n = 46) and ex-welders (n = 21). Each group was separately referenced with never-welders. The Kampmann clearance was within normal limits in all workers and not related to welding exposure. However, the urinary concentration of the majority of proteins was 1.5 to 3.0 times higher in both stainless steel and mild steel welders. The number of welding years taken as a measure of cumulative welding exposure was not related to levels of proteins in urine when adjusting for the effect of age. In addition, no alteration of urinary proteins was found among the ex-welders apart from slightly elevated albumin. This indicates that the apparent effect of welding on renal tubular function may at least partially be reversible. In conclusion, this study is in support of the hypothesis that metal welding may adversely affect renal tubular function, but it is questionable whether welding exposure has bearings as to occurrence of clinical significant kidney disease.

Early renal effects of occupational exposure to low-level hexavalent chromium

To detect early renal effects of occupational exposure to hexavalent chromium (Cr), urinary total proteins (U-TP), urinary albumin (U-Alb) and urinary retinol-binding protein (U-RBP) were determined in 166 male Cr platers and 106 male controls. The mean employment time in Cr plating for the platers was 12.6 years. Urinary Cr (U-Cr), which was determined as an index of Cr exposure, ranged from "not detected" to 19.91 micrograms/g creatinine in the platers. The U-Cr level was lower than those in other previous studies. Age-adjusted U-TP, U-Alb or U-RBP levels were not different between the platers and the controls. In the platers, a significant positive correlation was found between age-adjusted U-TP and U-Cr, but U-Cr had no significant relation to age-adjusted U-Alb or U-RBP level. Employment time had no effect on any age-adjusted urinary proteins. The Cr exposure may have been too low to induce definite renal dysfunction. Early renal effects of low-level Cr exposure may be mild, and may not be specific to renal function.

Chronic interstitial nephropathy after plasma cutting in stainless steel

Chromium is nephrotoxic in experimental animals. In subjects with acute chromium intoxication acute nephritis has been reported and renal function has been affected in chromium exposed workers with a high urinary chromium concentration. Chronic kidney disease after long term occupational exposure to chromium has, however, not been reported previously. A case report is presented concerning a 48 year old man who was diagnosed with chronic interstitial nephropathy. He had worked for nine years as a plasma cutter of stainless steel and had thereby been exposed to smoke containing chromium. At the time of diagnosis his blood chromium concentration was seven times higher and his urinary chromium concentration six times higher than reference values. Taking into account the nephrotoxicity of chromium and the high chromium burden of this patient it is considered likely that his exposure to smoke from plasma cutting of stainless steel was the cause of his chronic interstitial nephropathy.

Urinary N-acetyl-beta-D-glucosaminidase and beta-aminoisobutyric acid in workers occupationally exposed to metals such as chromium, nickel, and iron

To examine the relationships between the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) and beta-aminoisobutyric acid (AIBA) as a metabolite of thymine, and exposure to chromium, nickel, and iron, we determined these parameters in 58 workers engaged in the cutting and grinding of stainless steel or iron-steel plates. A significant increase in urinary NAG activity or urinary AIBA excretion was found in some of these workers. However, we could not find a significant positive correlation between the urinary excretion of NAG or AIBA and the urinary concentration of chromium, nickel, or iron as an indicator of internal dose.

Biomonitoring of genotoxic exposure among stainless steel welders

A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G. Environmental monitoring of welding fumes and selected metal oxides, biomonitoring of chromium and nickel in serum and urine and mutagenic activity in urine, and evaluation of semen quality were also done. Manual metal arc (MMA) welding and tungsten inert gas (TIG) welding were the dominant welding processes. A higher frequency of chromosomal aberrations, classified as translocations, double minutes, exchanges and rings, was observed in stainless steel welders than in non-welders. SCE was lower in welders working with both MMA and TIG welding than in reference persons. N-Acetoxy-N-acetylaminofluorene (NA-AAF)-induced UDS was lower in 23 never-smoking welders than in 19 unexposed never-smokers. Smoking was a confounding factor resulting in significantly higher CA, SCE, NA-AAF binding to DNA and mutagenic activity in urine. Age was also a confounder: CA, SCE, NA-AAF binding to DNA and UDS increased significantly with age. No significant correlation between SCE and CA or between CA and UDS was found. UDS decreased significantly with increasing lymphocyte count and a higher lymphocyte count was seen in MMA welders than in reference persons and in smokers than in non-smokers. Differences in the composition among lymphocytes in exposed persons compared with non-exposed are suggested. MMA welding gave the highest exposure to chromium, an increased number of chromosomal aberrations and a decrease in SCE when compared with TIG welding. Consequently improvements in the occupational practice of stainless steel welding with MMA is recommended.

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.

Renal function of chrome-plating workers and welders

The influence of occupational exposure to water-soluble chromium (VI) on renal function was examined. In male chrome-plating workers (n = 29), stainless steel welders (n = 45), boilermakers (n = 18) and a control group of workers (n = 71), the level of chromium in the urine (Cr-U), the chromium clearance, and sensitive renal function parameters were determined. The glomerular-function parameters of the chrome-plating workers (Cr-U 1 to 34 micrograms/g creat) and welders (Cr-U 1 to 62 micrograms/g creatine) appeared to differ from those of the boilermakers (Cr-U 0.3 to 1.5 micrograms/g creatine) and controls (Cr-U 0.1 to 2 micrograms/g creatine). The renal function parameters were not related to chromium concentration in the urine or to chromium clearance.

Exposure to welding fumes and chronic renal diseases, a negative case-referent study

It was observed that some patients with glomerulonephritis or interstitial nephritis were welders. A hypothesis that welding fumes were an occupational hazard was put forward and initiated the following case-referent study. 143 cases were defined as living males, age 25 to 65 years, with renal disease which caused renal biopsy from 1976-1982. Three population-based referents for each case were selected from the national register of the total population matched by sex, age and community. Exposure was assessed by means of a questionnaire. Only 7% of the cases and 12% of the referents did not answer the questionnaire. There were no differences in exposure rates between cases and referents, even if exposure restrictions were applied. The power of the case-referent study was high.