Heavy metals in welders' urine
Heavy metals in urine of welders. Urine test consisting of :
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Examination of a large group of welders found elevated levels of metals such as arsenic, nickel, zinc, chromium, copper, barium and iron in the urine of several employees. The company doctor found data on the health effects of exposure to arsenic, nickel and chromium, but not iron, copper, barium and zinc. He asked for advice because the company's management was concerned. What could he report to employees and management?
A good and recent overview of the health effects of welding has appeared in the latest edition of Hunters Diseases of Occupations [Grant 2001]. This bible of occupational diseases also compactly describes the occupational toxicology of heavy metals.
Determination of heavy metals in urine is a form of biological monitoring that can be of added value in certain situations to supplement environmental monitoring [Bos, 1998]. For example, in new or changed work situations if environmental measurements indicate elevated air concentrations. Biological monitoring or Biomonitoring says something about the exposure and thus the potential risk, but nothing about the clinical effect.
An elevated value of metals in the urine can only be interpreted if a few things are known about the toxicokinetics of that metal. For example, copper is excreted in the body through the gallbladder and zinc through the intestinal wall. Thus, for these metals, urine concentration is not a good method of biological monitoring. Barium is excreted mainly through the intestine, but in part also in the urine. It is known from research that no health effects have been described in welders with urinary values up to 100µg/l [Zwiesche 1992].
Copper, zinc and iron are essential elements for the body that are mainly absorbed through diet. In specific metabolic diseases, accumulation of, for example, iron and copper has been described but this is not related to occupational exposure. The elements are harmful only if they fall on your head as a zinc, iron or copper container, according to our toxicologist.
Biomonitoring of lead should be done in the blood: elevation of lead in the urine indicates exposure to organic lead. Biomonitoring of chromium (Cr) and nickel (Ni) in urine may be useful in stainless steel welders.
Urine sampling should be done under strict, contamination-free conditions: outside the work area, washing hands before urine discharge, special spore metal-free tubes and the like.
Determination is difficult due to the high risk of contamination and should be done by a laboratory accredited for these determinations. For correction, the concentration should be calculated as micrograms/gram of creatinine. Reference values for chromium: normal < 1 µg/g creat for stainless steel welders up to 100 µg/g creat Reference value for nickel < 3 µg/g creat.
These considerations raise the question of the wisdom of conducting untargeted research on a group of welders. What does the researcher want to find out? Have any occupational health studies found evidence of increased risk? And before starting an investigation, realize the significance of abnormal values and devise a scenario in advance to move forward.
However, now that this investigation has been started, there needs to be clarity about the significance of these elevated values. If it is clear that there has been no contamination of the samples and the quality of the laboratory is not in doubt, consideration can be given to expanding the study to include a control group of non-exposed people, such as office workers. In the meantime, study of the occupational toxicology of these metals is useful for proper counseling and education. Limitation to the metals with known occupational toxicological risks seems appropriate.
Source: G.van der Laan, R.F.M.Herber
Grant HG McMillan: Welding, fumes and inhalation fevers in: PJ Baxter, PH Adams, TC Aw, A Cockroft, JM Harrington, editors. Hunters diseases of occupations 9th edition. Arnold, London, 2000.
Bos RP, Boogaard PJ, Herber RFM, Kort WLAM de, Monster AC, Pal TM. Biomonitoring, an indispensable occupational health and safety tool, part 1 definition of concepts and objective. TBV 1998:4: 103-9
Zschiesche W, Schaller KH, Weltie D. Exposure to barium compounds: an interventional study in arc welders. Int Arch Occup Environ Hlth 1992:64: 12-23