With the aim to determine the presence of individual nitro-PAH contained in particles in the atmosphere of Mexico City, a monitoring campaign for particulate matter (PM10 and PM2.5) was carried out in Northern Mexico City, from April 2006 to February 2007

Endoparasites can alter their hostʹs heavy metal concentrations by sequestering metals in their own tissues. Contracaecum spp. (a nematode), but not Drepanocephalus spathans (a trematode), were bioaccumulating mercury to concentrations 1.5 times above cormorant hosts. Nematodes did not have significantly greater stable nitrogen isotope values (δ15N) than their hosts, which is contradictory to prey–predator trophic enrichment studies, but is in agreement with other endoparasite–host relationships. However, Contracaecum spp. δ13C values were significantly greater than their hosts, which suggest that nematodes were consuming host tissues. Nematodes were accumulating and thus sequestering some of their cormorant hostsʹ body burden of methyl mercury; however, they were not dramatically reducing their hostsʹ accumulation of methyl mercury.