Pleural mesothelioma in New Caledonia: An acute environmental concern

Background: In 1991, a relationship was established between excess cases of pleural cancer in New Caledonia and a traditional lime, called “Pö”, to cover houses. Our study aimed to determine whether the Pö is the only cause of mesothelioma in New Caledonia. Methods: Eligible cases were pleural tumor diagnosed between 1984 and 2002 with histological diagnosis of mesothelioma. For each case, two controls were selected from the cancer registry. Cases and controls were compared for the ethnic groups and the places of residence. To identify environmental risk factors, we used first a qualitative analysis comparing villages with and without mesothelioma cases, then a linear regression including Pö, mining activity and serpentinite in surface soil. Results: Sixty-eight cases were included: 37 men and 31 women. Melanesians had the highest risk (OR = 16.18; 95% CI = [5.68; 49.64]) and 30% of the cases lived in Houailou (OR = 119). Mining activity and Pö were not significant risk factors. The existence of a significant relationship between soil containing serpentinite and mesothelioma was demonstrated (p = 0.017). The sex ratio close to 1 and the number of young cases are consistent with environmental exposure. Conclusion: Pö did not explain all cases; only serpentinite in the soil was identified as a significant risk factor. A research project has been initiated in the area around Houailou, with the objective of constructing a model taking into account: exposure to the Pö, exposure to airborne pollution by asbestos fibres at the place of residence, and occupational exposure. Epidemiological and geological investigations are underway.