J Med Assoc Thai 2009; 92 (12):115

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Health Risk among Asbestos Cement Sheet Manufacturing Workers in Thailand
Phanprasit W Mail, Sujirarat D , Chaikittiporn C

Objective: To assess asbestos exposure and calculate the relative risks of lung cancer among asbestos cement
roof sheet workers and to predict the incidence rate of lung cancer caused by asbestos in Thailand.

Material and Method:
A cross-sectional study was conducted in four asbestos cement roof factories. Both area
and personal air samples were collected and analyzed employing NIOSH method # 7400 and counting rule A
for all procesess and activities. The time weight average exposures were calculated for each studied task using
average area concentrations of the mill and personal concentrations. Then, cumulative exposures were
estimated based on the past nation-wide air sampling concentrations and those from the present study. The
relative risk (RR) of lung cancer among asbestos cement sheet workers was calculated and the number of
asbestos related lung cancer case was estimated.

The roof fitting polishers had the highest exposure to airborne asbestos fiber (0.73 fiber/ml). The
highest average area concentration was at the conveyor to the de-bagger areas (0.02 fiber/ml). The estimated
cumulative exposure for the workers performed studied-tasks ranged in between 90.13-115.65 fiber-years/ml
while the relative risk of lung cancer calculated using US. EPA’s model were 5.37-5.96. Based on the obtained
RR, lung cancer among AC sheet in Thailand would be 2 case/year.

In case that AC sheet will not be prohibited from being manufactured, even though only chrysotile
is allowed, the surveillance system should be further developed and more seriously implemented. The better
control measures for all processes must be implemented. Furthermore, due to the environmental persistence of
asbestos fiber, its life cycle analysis should be conducted in order to control environmental exposure of
general population.

Keywords: Asbestos exposure, Asbestos cement roof sheet, Risk assessment

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