The groundwater in Alsace, north of Mulhouse, has been contaminated by a complex mixture of substances—the main component of which is chloronitrobenzene—as a result of industrial accidents. In 2007, a detailed risk assessment conducted by one of the manufacturers, Rhodia, as part of the site’s decommissioning, did not conclude that there was a health risk. However, a critical analysis conducted by Cire Est revealed numerous scientific uncertainties in this work due to the absence of validated toxic reference values for the compounds predominantly found in the groundwater. Given the uncertainty regarding a potential health impact, the French Institute for Public Health Surveillance (ISP) requested the implementation of an epidemiological study in partnership with the Haut-Rhin Cancer Registry to investigate a health signal that might be linked to this pollution. The objective of this study was to investigate a difference in the incidence of the selected cancer sites between areas exposed to groundwater pollution and the Haut-Rhin department between 1988 and 2002. This exploratory study revealed a statistically significant difference in incidence across the study areas for only one of the cancer sites examined: lung cancer. For all other cancer sites studied, including the liver—the predominant target organ in toxicological studies—the SIRs do not differ significantly from 1. These results do not support the hypothesis that groundwater pollution in the northwest of Mulhouse has an impact on cancer incidence in the exposed population. Indeed, risk factors are well documented for lung cancer (tobacco use, air pollution), and differences in exposure to these factors among the studied population compared to the department’s general population may explain this small difference in incidence. Such observations are insufficient to be considered a health signal. Therefore, it does not appear necessary to continue epidemiological investigations. Furthermore, the Haut-Rhin Cancer Registry, which has been in operation since 1988, provides the necessary specific surveillance. (R.A.)