Mining activities in central Mexico generate 65 % of industrial pollutants from the country that are thrown into the environment.  These pollutants potentially represent a serious threat to both human and ecosystem health. On February 2006 we initiated a research project to quantify lead and arsenic concentrations in blood and feathers of mostly insectivorous passerine birds in “Villa de la Paz”, a region in the central Mexican state San Luis Potosí, that has being heavy exploited for several decades.   We used ornithological mist nets to capture birds.  Then we took feather and blood samples before releasing the organisms.  To date we have captured and banded 130 birds from 41 species and we have taken 22 blood and 90 feather samples from 5 study areas located at increasing distances from the pollution source.  We have already started to analyze our samples with atomic absorption spectroscopy techniques; lead concentrations in blood samples ranged from 8.11 to 29.32 µg/dl.  These results are considerably higher than those reported on previous studies.  We are currently obtaining additional blood and feather samples, and quantifying arsenic contents in our existing feather samples, and plan on presenting these additional data during the ESA conference.  Although none of the parameters at the population and community levels that we have estimated so far (sex ratios, age structure, body weight, and species richness) seem to be correlated to lead contents in our blood samples, sample sizes are still small and will substantially increase during the upcoming months.