Spatial and temporal assessment of health risks associated with exposure to nitrates from shallow well water in West Africa

Abstract

This study focused on estimating the health risks of nitrate from shallow well water in Agboville's city, Côte d'Ivoire. 100 samples of 50 wells were collected to analyze nitrate presence during one year in two major seasons. Probabilistic methods of hazard quotient were used to assess the health risks due to nitrate within different zones delineated in relation to the demographic and topographic situation of the areas. The mean nitrate levels of each zone during dry season were below the World Health Organization (WHO, 2011) limit value (i.e., 50 mg L−1), whereas for those of the wet season, the values of some sites were higher, but their average remained below this WHO reference, excluding of the low-slope area (i.e., zone 2 with 75.40 ± 68.33 mg L−1). During dry season, all the hazard quotient (i.e., HQ50 and HQ95) values were below to 1, as were HQ50 values in wet season, except for children in the low-slope area (i.e., zone 2). All HQ95 values were nearly greater than 1 during the wet season. Only, Hazard quotient using acceptable daily intake (HQADI) value at the 5% highly-exposed group of the strongest slope area (zone 4) was less than 1 in the wet seasons. It noted that the elevated HQ95 values would indicate a high risk of nitrate during the rainy season. Otherwise, HQ50/50 values determined according to WHO 2003 values were higher than 1 in rainy season, thereby underscoring that the elevated risk of contracting some diseases such as methemoglobinemia. Finally, a sanitation improvement in the study area could be an alternative method to reduce nitrate levels in well water as well as a reduction of the HQ50/50 in rainy season