Regression model of partial pressures of PCBs, PAHs, and organochlorine pesticides in the Great Lakes' atmosphere.

The gas-phase concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides have been measured at six sites around the Great Lakes every 12 days since the early 1990s as part of the Integrated Atmospheric Deposition Network. After converting the concentrations into partial pressures, data from all of the sites were combined and fitted using a multiple linear regression equation that included time (indicating the effect of a chemical's regulation), atmospheric temperature (indicating seasonality of use or release), the human population within a 25 km radius of the site (indicating the effect of urbanization) and wind speed and wind direction (indicating the source of the chemical). The atmospheric levels of lindane (gamma-HCH), DDTs, endosulfans, and chlordanes were largely related to seasonality, with much higher levels in the warm summer months. The levels of SigmaPCBs, SigmaPAHs, SigmaDDTs, and chlordanes were related to urbanization (this was a secondary factor for the latter two), a result that was unexpected for the two pesticides. The levels of only two compounds, alpha- and gamma-HCH, decreased rapidly as a function of time; conversely, most other compounds are declining at much slower rates. Wind speed and wind direction were statistically significant but unimportant variables for most of the compounds.