Understanding the Vegetable Contamination Process with Parasites from Wastewater Irrigation and Its Impact on Human Health in Hidalgo, Mexico

The use of untreated municipal wastewaters for irrigating agricultural crops negatively affects human health. Thus, the sewage effluent from the city of Pachuca, in the state of Hidalgo, Mexico, used for agricultural purposes was the most important reason to undertake this research work, whose main objective was to understand the process that involves its current use as irrigation water, and the potential harm to human health because the raw vegetables produced using this irrigation scheme are being consumed by the general public. The content of fecal coliforms and helminth eggs in wastewaters were determined and the level of parasitological contamination of vegetables and the potential number of people affected was estimated due to the consumption of raw produce without proper pretreatment, a common practice in Mexico. The potential level of parasitological contamination of vegetables was estimated by analyzing bibliographic data collected under similar climatic and technological conditions as in Pachuca. Results indicate that the level of wastewater contamination from fecal coliforms in Pachuca was 5000 times higher than the maximum permissible level based on Mexican standards for irrigation waters, and for Ascaris lumbricoides L. and Hymenolepis diminuta (Rudolphi) eggs up to 64 times. The number of persons potentially infected through consumption of raw vegetables irrigated with this contaminated water was estimated to be 169,000 annually.