ENVIRONMENTAL EXPOSURE TO CARCINOGENIC FIBERS DUE TO SERPENTINITE PAVED ROADS IN NEW CALEDONIA: LESSONS IN ENVIRONMENTAL EPIDEMIOLOGY AND IN PREVENTION

The term asbestos designates 6 fibrous minerals that are used by industry and responsible for lung cancers and malignant mesothelioma. In 1980, mineralogical analysis showed the presence of asbestos in nickel ore specimens from New Caledonia (NC). However, a study established in 1995 a relationship between excess cases of pleural cancer in NC and a traditional house whitewash called Pö.

In order to study the causes of environmental exposure to carcinogenic fibers in NC, we analyzed the spatial and temporal variation of mesothelioma and its association with environmental factors.

The analysis of cancer incidence in NC for the past 30 years showed an over incidence of lung cancers and mesothelioma in both sexes. Melanesians had the highest mesothelioma risk (OR = 16.18; 95% CI = [5.68; 49.64]) compared to Europeans. The sex ratio close to 1 and the number of young cases were consistent with environmental exposure. A significant mesothelioma cluster grouped 18 tribes (31 observed cases vs 8.12 expected cases, p=0.001). No significant temporal clusters were identified. The ecological analyses identified serpentinite on roads as the greatest environmental risk factor: OR = 495.0, 95%CI: 46.2–4679.7; multivariate IRR=13.0, 95%CI: 10.2-16.6. We noticed the presence of numerous serpentinite quarries in the highest risk areas, whose main fibrous mineral was antigorite. The association of mesothelioma with serpentines, particularly antigorite, was stronger than for amphiboles. Living on a slope and close to dense vegetation appeared protective. The use of whitewash was not associated with mesothelioma incidence.

This study demonstrated that the use of serpentinite to cover roads is a major environmental risk factor for mesothelioma and that antigorite may release carcinogenic fibers. Most of the natural fibrous minerals are not known as asbestos and so are not regulated. They pose an environmental risk when their fibers are released in the air by weathering or by human activities, as it is the case in the Western US with erionite gravels.