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, as the company's management was concerned. What could he report to employees and management?
A good and recent overview of the effects of welding on health 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 may have added value in certain situations as a supplement to environmental monitoring [Bos, 1998]. For example, in new or changed work situations if environmental measurements show that elevated air concentrations are present. Biological monitoring or Biomonitoring says something about the exposure and thus about the potential risk, but nothing about the clinical effect.
An elevated value of metals in the urine can only be interpreted if something is 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, the concentration in the urine is not a good method of biological monitoring. Barium is excreted mainly through the intestine, but part also in the urine. It is known from research that no health effects have been described in welders with urine 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 only harmful if they fall on your head as a zinc, iron or copper container, according to our toxicologist.
Biomonitoring of lead should be in the blood: elevation of lead in the urine indicates exposure to organic lead. Biomonitoring of chromium (Cr) and nickel (Ni) in the urine may be useful in stainless steel welders.
Sampling of urine should be done under strict, contamination-free conditions: outside the working area, washing hands before urination, special sporemetal-free tubes and the like.
Determination is difficult due to the high risk of contamination and must 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 studies in a group of welders. What does the researcher want to find out? Have there been indications of increased risk in occupational hygiene studies? Before starting an investigation, realize what the significance of abnormal values is and think of a scenario in advance in order to move forward.
However, now that this investigation has been started, the meaning of these elevated values must be clarified. If it is clear that no contamination of the samples has taken place and the quality of the laboratory is not in doubt, it can be considered to extend the study with a control group of non-exposed persons, for example office workers. In the meantime, it is useful to study the occupational toxicology of these metals in order to provide good advice and information. Restriction to metals with known occupational toxicological risks seems appropriate.
Source: G.van der Laan, R.F.M.HerberLiterature
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 tool, part 1 definition and objective. TBV 1998:4: 103-9Zschiesche
W, Schaller KH, Weltie D. Exposure to barium compounds: an interventional study in arc welders. Int Arch Occup Environ Hlth 1992:64: 12-23