Monthly averages of arsenic, cadmium, and lead PMx measured with the MOUDI sampler at the Hayden site from December 2008 to November 2009. The size ranges are defined as follows: PM<9.9 is the summation of cutpoint diameters 9.9 and 18 μm, PM3.1-9.9 is the summation of cutpoint diameters 3.1 and 6.1μm, PM1-3.1 is the summation of cutpoint diameters 1 and 1.8μm, and PM<1 is the summation of cutpoint diameters lower than 1μm.