The following visualization displays the Diesel Particulate Matter readings (colored markers) along with the number of asthma-related hospital visits for children age 0 – 17 for select Los Angeles ZIP codes.
According to Dieselnet.com:

Diesel particulate matter (DPM) is the most complex of diesel emissions. Diesel particulates, as defined by most emission standards, are sampled from diluted and cooled exhaust gases. This definition includes both solids, as well as liquid material which condenses during the dilution process. The basic fractions of DPM are elemental carbon, heavy hydrocarbons derived from the fuel and lubricating oil, and hydrated sulfuric acid derived from the fuel sulfur. DPM contains a large portion of the polynuclear aromatic hydrocarbons (PAH) found in diesel exhaust.

Clicking on any of the DPM markers within FactLook brings up additional data, including percentages of ozone and particulates.