Introduction The impact of EU directives and national occupational health and safety legislation has been hardly assessed. In the current study, we use data collected by occupational health physicians for more than 20 years to investigate whether or not changes in legislation influence the percentage of smokers among employees.

Method Data of health surveillance between 1993 and 2015 were considered, and included information about smoking habit, age, sex, and year of investigation of on average 190.000 workers per year (SD = 46.416). The most important changes in Belgian and European legislation regarding smoking were listed up by means of a literature search. First, the impact of legislation on the percentage of smokers was assessed graphically. Next, segmented logistic regression analysis was used to model the impact of several changes in legislation on the trend in smoking percentages, while controlling for sex and age.

Results Between 1993 and 2015 the percentage of smokers decreased from 32,41% to 29,89%. We observed the largest decrease (4,14%) in percentage of smokers between 2000 and 2004 (resp. 32,48% and 28,34%), starting one year after the ban on cigarette advertisement and during the legislation regarding health warnings on cigarette packs in 2002. Before and after this time period, the percentage of smokers remained rather stable over time. Segmented logistic regression supported these findings, while controlling for sex and age (slope before 2000 = 0.004, p-value = 0.001; slope between 2000 and 2004 = −0.042, p-„value = 0.000; slope after 2004 = 0.003, p-value = 0.000). The effect of both changes in legislation could not be distinguished.

Conclusion Legislation seems to influence smoking behaviour in workers, leading to a drop in percentage of smokers between 2000 and 2004. Legislation changes that probably were most effective include the ban on advertisement and the health warnings on cigarette packs.