Occurrence of airborne enteric bacteria in Mexico city

Summary An investigation of microbial air quality in the area of the National Autonomous University of Mexico, located in the southern part of Mexico City, was conducted for one year. Ambient outdoor concentrations and size distribution of airborne bacteria were measured, 130 samples were taken at noon, using an Andersen 6 stage sampler, located 2 m above ground level. Concentration ranges and colony-forming units per cubic meter of air (CFU m^–3) found, were as follows:14 to 12999 for total bacteria, No growth (NG) to 55 for coliform bacteria, NG to 11 for fecal coliform and NG to 10 for fecal Streptococci.Bacteria associated with the potentially respirable fraction (0.65 to 4.7 µm) averaged 37% and 9% for total bacteria and coliform bacteria respectively. In 23% of the samples, coliform bacteria were recovered, with higher incidences during dry season. The most common of these were:Escherichia coli (15%), followed bySerratia (13%) andEnterobacter (10%),The total bacteria correlated significatively (p<0.05) with the following parameters: particulate matter smaller than 10 µm (PM₁₀) (r=0.40), total suspended particulates (TSP) (r=0.26), daily variation of temperature (r=0.18), and vapor pressure (r=–0.16). These relationships indicate that fecal soil pollution could affect air quality with potential health risks.