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Friday, 22 April 2011 10:27

Case Studies: Prevention of Occupational Dermatosis Among Workers Exposed to Cement Dust

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The most common form of occupational dermatosis to be found among construction workers is caused by exposure to cement. Depending on the country, 5 to 15% of construction workers—most of them masons—acquire dermatosis during their work lives. Two types of dermatosis are caused by exposure to cement: (1) toxic contact dermatitis, which is local irritation of skin exposed to wet cement and is caused mainly by the alkalinity of the cement; and (2) allergic contact dermatitis, which is a generalized allergic skin reaction to exposure to the water-soluble chromium compound found in most cement. One kilogramme of normal cement dust contains 5 to 10 mg of water-soluble chromium. The chromium originates both in the raw material and the production process (mainly from steel structures used in production).

Allergic contact dermatitis is chronic and debilitating. If not properly treated, it can lead to decreased worker productivity and, in some cases, early retirement. In the 1960s and 1970s, cement dermatitis was the most common reported cause of early retirement among construction workers in Scandinavia. Therefore, technical and hygienic procedures were undertaken to prevent cement dermatitis. In 1979, Danish scientists suggested that reducing hexavalent water-soluble chromium to trivalent insoluble chromium by adding ferrous sulphate during production would prevent chromium-induced dermatitis (Fregert, Gruvberger and Sandahl 1979).

Denmark passed legislation requiring the use of cement with lower levels of hexavalent chromium in 1983. Finland followed with a legislative decision at the beginning of 1987, and Sweden and Germany adopted administrative decisions in 1989 and 1993, respectively. For the four countries, the accepted level of water-soluble chromium in cement was determined to be less than 2 mg/kg.

Before Finland’s action in 1987, the Board of Labour Protection wanted to evaluate the occurrence of chromium dermatitis in Finland. The Board asked the Finnish Institute of Occupational Health to monitor the incidence of occupational dermatosis among construction workers to assess the effectiveness of adding ferrous sulphate to cement in order to prevent chromium-induced dermatitis. The Institute monitored the incidence of occupational dermatitis through the Finnish Register of Occupational Diseases from 1978 through 1992. The results indicated that chromium-induced hand dermatitis practically disappeared among construction workers, whereas the incidence of toxic contact dermatitis remained unchanged during the study period (Roto et al. 1996).

In Denmark, chromate sensitization from cement was detected in only one case among 4,511 patch tests conducted between 1989 and 1994 among patients of a large dermatological clinic, 34 of whom were construction workers. The expected number of chromate-positive construction workers was 10 of 34 subjects (Zachariae, Agner and Menn J1996).

There seems to be increasing evidence that the addition of ferrous sulphate to cement prevents chromate sensitization among construction workers. In addition, there has been no indication that, when added to cement, ferrous sulphate has negative effects on the health of exposed workers. The process is economically feasible, and the properties of the cement do not change. It has been calculated that adding ferrous sulphate to cement increases the production costs by US$1.00 per tonne. The reductive effect of ferrous sulphate lasts 6 months; the product must be kept dry before mixing because humidity neutralizes the effect of the ferrous sulphate.

The addition of ferrous sulphate to cement does not change its alkalinity. Therefore workers should use proper skin protection. In all circumstances, construction workers should avoid touching wet cement with unprotected skin. This precaution is especially important in initial cement production, where minor adjustments to moulded elements are made manually.

 

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