Residual oil combustion: a major source of airborne nickel in New York City.

On the basis of previous observations that: (1) both the nickel (Ni) concentration in ambient air fine particulate matter (PM(2.5)) and daily mortality rates in New York City (NYC) were much higher than in any other US city; and (2) that peaks in Ni concentration was strongly associated with cardiac function in a mouse model of atherosclerosis, we initiated a study of the spatial and seasonal distributions of Ni in NYC and vicinity to determine the feasibility of productive human population-based studies of the extent to which ambient fine particle Ni may account for cardiovascular health effects. Using available speciation data from previous studies at The New York University, Environmental Protection Agency's Speciation Trends Network; and the Interagency Monitoring of Protected Visual Environments network, we determined that Ni in NYC is on average 2.5 times higher in winter than in summer. This apparent seasonal gradient is absent, or much less pronounced, at NJ and CT speciation sites. Ni concentrations at a site on the east side of Manhattan and at two sites in the western portion of the Bronx were a factor of two higher than at a site on the west side of Manhattan, or at one at Queens College in eastern Queens County, indicating a strong spatial gradient within NYC. We conclude that the winter peaks of fine particle Ni indicate that space heating, which involves the widespread reliance on residual oil combustion in many older residential and commercial buildings in NYC, is a major source of ambient air Ni. Epidemiologic studies based on data generated by a network of speciation sites throughout NYC could effectively test the hypothesis that Ni could account for a significant portion of the excess mortality and morbidity that have been associated with elevated mass concentrations of PM(2.5).