Effectiveness of the European chromium( vi ) directive for cement implementation on occupational allergic contact dermatitis occurrence: assessment in France and the U.K.

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Dear Editor, Hexavalent chromium is the main sensitizer in wet cement and a common cause of occupational allergic contact dermatitis (OACD), especially among workers in the construction industry.1,2 The European chromium(vi) directive,3 which transposed into national regulations in France and the U.K. in May and January 2005, respectively, prohibits selling or use of hydrated cement with more than 0·0002% of chromium. This was achieved through the addition of ferrous sulfate to the dry product, allowing reduction of chromium(vi) to chromium(iii), which is less sensitizing. Previous studies from national surveillance systems on contact allergy have described a temporal decrease in the prevalence of chromate sensitization in the general population.4,5 However, their analyses did not provide information on the actual sources of chromium and their occupational relevance. Conversely, chromium OACD still remains a problem in some countries, such as Australia.6 In the U.K. a surveillance network collects incident reports of work‐related skin diseases, including data on the suspected causal agent(s), occupation and industry. EPIDERM belongs to this family of work‐related disease surveillance schemes known as The Health and Occupation Reporting Network (THOR). Since 2001 in France, the National Network for Vigilance and Prevention of Occupational Diseases (RNV3P, Réseau National de Vigilance et de Prévention des Pathologies Professionnelles) has continuously monitored new medically certified occupational diseases, including OACD, assessed by experienced occupational medical experts, most of the time dermatologists or allergists, their diagnosis being based on positive patch test results and their occupational relevance.7 The aim of this paper is to assess the impact of the implementation of the European directive on OACD occurrence attributed to chromium in cement notified in the RNV3P and THOR.8 The study was designed as a controlled ‘before and after’ study. It compares the change in the number of incident notified cases per month in each network in target groups (expected to be impacted by the regulation) and in a comparison group (not expected to be impacted by the regulation), before and after the regulation [respectively time 1 (2002–2004) and time 3 (2006–2010); the year 2005 (time 2) corresponds to the intervention year]. The postintervention change in incidence of reported OACD is described by the ratio of incidence in time 2 and time 3, respectively, relative to that in time 1. This ratio can be regarded as an incidence rate ratio (IRR) considering rate denominators that are constant over time.9 We identified two classes of exposure that could be impacted by the intervention: (i) cement, most likely chromate in cement, and (ii) chromate in construction occupations. The resulting case groups 1, 2 and 3 were considered to be probably or certainly associated with occupational exposure and expected to be affected by the intervention, while group 4 was chosen as a control group (Table 1). In order to compare the change in incidence in the target groups (case groups 1–3 and the comparison group), we estimated the ratios of two IRRs (RIRRs). Year 2001 was excluded to avoid including prevalent cases during the first year of the network. Statistical analyses were performed using R software (v3·0·1; https://www.r-project.org) and Stata 13 (StataCorp, College Station, TX, U.S.A.). Statistical significance was defined as P < 0·05. Definition of cases of occupational allergic contact dermatitis (OACD) grouped according to their exposures and occupations in France and the U.K French construction workers included builders, bricklayers and stonemasons, concrete placers, concrete finishers and related workers, carpenters and joiners, building frame and related trades workers not elsewhere classified, roofers, floor layers and tile setters, plasterers, and construction labourers. U.K. construction workers included bricklayers and masons, roofers, roof tilers and slaters, carpenters and joiners, construction trades not elsewhere classified, plasterers, floorers and wall tilers, road and rail construction operatives, construction operatives not elsewhere classified, labourers in building and woodworking trades, and labourers in other construction trades not elsewhere classified. Definition of cases of occupational allergic contact dermatitis (OACD) grouped according to their exposures and occupations in France and the U.K French construction workers included builders, bricklayers and stonemasons, concrete placers, concrete finishers and related workers, carpenters and joiners, building frame and related trades workers not elsewhere classified, roofers, floor layers and tile setters, plasterers, and construction labourers. U.K. construction workers included bricklayers and masons, roofers, roof tilers and slaters, carpenters and joiners, construction trades not elsewhere classified, plasterers, floorers and wall tilers, road and rail construction operatives, construction operatives not elsewhere classified, labourers in building and woodworking trades, and labourers in other construction trades not elsewhere classified. All procedures performed involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The RNV3P network received the approval of the national board enforcing data protection legislation (CNIL, Commission Nationale de l'Informatique et des Libertés). The EPIDERM network, which is part of THOR, received multicentre research ethics committee approval (02/8/72). In the French network, during the postdirective period (2006–2010) compared with the predirective period (2002–2004), there was a significant increase in occurrence of all OACD (IRR 1·09). However, the increase was confined to the comparison group (IRR 1·14), whereas occurrence of OACD related to cement, chromate or both in exposed occupations decreased (Table 2). These decreases were significant relative to the comparison (unexposed) group (RIRRs 0·49, 0·62 and 0·58 for groups 1, 2 and 3, respectively). Estimated changes in the incidence of occupational allergic contact dermatitis (OACD) after the European cement directive (2005) in France (n = 3357) and the U.K. (n = 3818) RIRR, ratio of incidence rate ratios, defined as (incidence during time 2 or 3 ÷ incidence during time 1 for target group) / (incidence during time 2 or 3 ÷ incidence during time 1 for comparison group). aIncidence rate ratio (IRR) in time 2 (2005) compared with time 1 (2002–2004). For each group (1–4), monthly case counts were analysed using a two‐level negative binomial regression model with random effects as previously described.8,9 The two‐level model assumed a hierarchical structure with time nested within centre. The main predictor of interest, time period, was treated as a categorical variable as defined above. A further covariate was month of year to allow for seasonal changes in reporting. For the U.K. data other covariates specific to the network features were included as described previously.8,bFor RIRRs comparing IRR between each group (1–3) and all other OACD, interaction terms representing the product of the dummy time variable and the group (comparison/target) variables were included in the model. The comparison of change between groups is expressed as the RIRR for the time periods specified.9cIRR in time 3 (2006–10) compared with time 1 (2002–2004). Estimated changes in the incidence of occupational allergic contact dermatitis (OACD) after the European cement directive (2005) in France (n = 3357) and the U.K. (n = 3818) RIRR, ratio of incidence rate ratios, defined as (incidence during time 2 or 3 ÷ incidence during time 1 for target group) / (incidence during time 2 or 3 ÷ incidence during time 1 for comparison group). aIncidence rate ratio (IR

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