Water quality in the karstic coastal municipality of Hunucmá, Yucatán, México. Risks to human health

A study was conducted to characterize water quality during the dry and rainy periods in the municipality of Hunucmá, Yucatán, México, by determining the concentrations of toxic metals, nitrates, and coliforms, in samples taken from twelve household wells and three drinking water distribution wells. The state of Yucatán has a karst aquifer of high vulnerability to groundwater contamination. The water samples were analyzed by Cold Vapor Atomic Absorption Spectroscopy to quantify Hg, and Inductively Coupled Plasma Mass Spectrometry to quantify Cr, Cu, Zn, As, Cd, and Pb. The highest detected metal concentrations were 0.016 ppm of Zn, 0.0014 ppm of As, 0.0005 ppm of Cd, 0.0011 ppm of Pb, and 0.0023 ppm of Hg. Although national standard values are not exceeded, there are risks to human health due to bioaccumulation from chronic exposure through contaminated water and food. In addition, nitrate levels ranging from 4 to 8.5 mg/L in the dry period and from 3.2 to 7.8 mg/L in the rainy period were found. These concentrations are close to the maximum allowed limit. The average for fecal coliform count was 900 MPN/100 ml, represent high risks to human health.