Drexler H, Schaller KH, Nielsen J et al, Efficacy of measures of hygiene in workers sensitised to acid anhydrides and the influence of selection bias on the results, J Occup Environ Med, 1999;56:202-205,

BOHRF Original Authors' Main Conclusions

The original authors' main conclusions are taken from Abstract, Results and Discussion. They are decided upon by the authors of the BOHRF occupational asthma guidelines and form part of the guidelines.

An investigation with 110 workers exposed to hexahydrophthalic acid anhydride (HHPA) and methyltetrahydrophthalic acid anhydride (MTHPA) was carried out in July 1991 and in December 1991, the hygiene conditions at the plant were improved. In November 1995 a second investigation of 84 people was performed. The relative risk of people sensitised in 1991 of leaving the plant between 1991 and 1995 was 2.6 compared with people without any sign of sensitisation. The percentage of people identified as sensitised in 1991, who were still working at the plant and came to the second investigation, was higher than for people without evidence of sensitisation. Of the 6 people with clinically relevant sensitisation confirmed by a challenge test in 1991, 5 were still at their workplace. From 1991 they were only exposed to MTHPA at a reduced concentration and all of them reported fewer symptoms than in 1991. Authors concluded that in Cross-sectional studies there is a selection bias with a risk of underestimating the incidence of allergic diseases. The results further suggest that the improved hygiene conditions probably had a positive effect on the symptoms in sensitised people.

BOHRF Associated Evidence Statements

The BOHRF occupational asthma guidelines state that this reference is associated with the following evidence statements

*** 2++ Reducing airborne exposure reduces the number of workers who become sensitised and who develop occupational asthma.

Non Bohrf Information

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