Centers
Daan Huizer, MSc,1 Ton Spee PhD,2 Mieke Lumens PhD,1 and Hans Kromhout PhD, Published in:
American Journal of Industrial Medicine 2010 Jun;53(6):628-34
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Abstract
Background Construction workers are educated at vocational training centers before they begin their working lives. Future bricklayers and their instructors are exposed to respirable dust and possibly to hazardous respirable crystalline silica from trial mortar.
Method Thirty-six personal air samples were collected at 6 training centers to estimate exposure to respirable dust for both students and teachers. A selection of 22 samples was analyzed for crystalline silica.
Results Average respirable dust exposures ranged from 0.59 mg/m3 for teachers to 1.45 mg/m3 for students performing recycling and cleaning tasks. In 45% of the analyzed samples, respirable crystalline silica was detected. Exposure to silica remained below the Dutch OEL (75 μg/m3). Exposure was significantly less for teachers than it was for students. This effect was found in both types of vocational training centers that are present in the Netherlands. Dry sweeping, as performed at all locations in this study, contributed considerably to the exposure to respirable dust. A first step in reducing exposure to dust and silica at training centers would therefore be to avoid dry sweeping. The presence of a dust extraction system, although not optimally designed, also significantly lowered exposure.
Conclusions To assess a construction worker’s lifetime exposure to respirable dust and crystalline silica, the vocational training period should also be taken into account.
Several epidemiological studies have shown that time since first exposure can be an important risk factor for chronic health effects.
3.1 Introduction
Exposure to respirable crystalline silica in the construction industry has been widely recognized as a health hazard (Linch et al., 1998; Linch, 2002; Steenland, 2005). It is strongly associated with the incidence of silicosis, and because it has also been classified as a human carcinogen, exposure levels should be as low as possible (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, 1997).
The awareness of the hazardous properties of respirable crystalline silica in the construction industry has increased globally over the past years (Lumens and Spee, 2001, Flanagan et al., 2006). Subsequently, occupational exposure limits (OELs) have been lowered in many countries.
As a result, control measures are now available for many tasks in the construction industry; however, control measures do not always guarantee that exposure levels will be safe (Linch, 2002; Rappaport et al,. 2003; Flanagan et al.,
Exposure to Respirable Dust and Silica in Bricklaying Education at Dutch Vocational Training Centers
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2006). Exposure levels in the construction industry still frequently exceed the limits (Flynn and Susi, 2003; Tjoe et al., 2003; Flanagan et al., 2006). Also, workers’ behavior has been shown to be a relevant determinant of exposure (Lumens and Spee, 2001).
From another perspective, it is not only the level of exposure that is relevant to avoiding adverse health effects, but also the accumulated exposure over someone’s working life in the case of health effects due to chronic exposure. As OELs are based on a working life of 40 years, special attention should be paid to exposure starting at an early age, which may extend the working life exposure period. Young people (ages 13 to 16 years) have immature lungs that are especially vulnerable to damage from foreign particles, and many construction workers begin their trades in their mid-teens.
The adverse health effects that occur in a later stage of the working life because of exposure at a young age show the relevance of studying a young population (Kreuzer et al., 1999). This applies to many sectors with exposure to agents with chronic health effects.
Several authors have studied health effects from hazardous substances among apprentices in vocational training programs like car painting (Eifan et al., 2005), the food industry (Gautrin et al., 2002; Walusiak et al., 2002; Walusiak et al., 2004), and welding (El-Zein et al., 2003).
In this study, we focused on exposure to respirable dust and its crystalline silica content among students in vocational training centers in the Netherlands where future construction workers are educated and trained. Exposure to respirable dust and crystalline silica at training centers (mainly indoors) has, to our knowledge, not been studied, as most studies have focused on exposure at construction sites.
Concern about dust exposure in vocational schools prompted the establishment of a working group, which was initiated by stakeholders representing building materials production, education institutions, and Arbouw, the Dutch institute for working conditions in the construction industry. As a first step, a questionnaire was distributed among all known training centers (N = 340) to get an indication of health complaints related to dust exposure and to list the main characteristics of the schools.
The response to the questionnaire was low (22%), which could be partly because it was unknown how many of these training centers actually offered bricklaying education.
In the Netherlands, two types of bricklaying training centers are present:
governmental schools and apprentice workshops. Many young bricklayers take part in an apprentice system in which they work 3 or 4 days and go to school 1 or 2 days.
The apprentice system lasts 2–4 years. During these years young bricklayers spend 5–32 hr per week at school, depending on their school and the phase of education they are in. This system is maintained cooperatively by the construction companies. The main differences between governmental schools and apprentice workshops are the characteristics of the school buildings. Apprentice workshops tend to be much more spacious than the “classical” school buildings of governmental schools. Volumes of
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classrooms therefore differ considerably.
Although it became clear from the questionnaire that there was concern about exposure to dust, it also showed limited use of exposure control measures such as vacuum cleaning, wetting of the floor, and controlling of the humidity of the classrooms. Furthermore, limited use of personal protective equipment (about 20%
of the respondents) was reported.
Based on the outcomes of the questionnaires, we decided to perform an exposure survey to assess exposure to respirable dust and respirable crystalline silica at 6 different bricklaying training centers, 4 from governmental schools and 2 from apprentice workshops. We focused on exposure of both students and teachers during bricklaying and related activities. Possible control measures that had already been taken to reduce exposure were also considered.