Air Pollution measures the particulate matter in the air. It reports the average daily density of fine particulate matter in micrograms per cubic meter. Fine particulate matter is defined as particles of air pollutants with an aerodynamic diameter less than 2.5 micrometers (PM2.5).From EPHT: The monitoring data comes from the U.S. Environmental Protection Agency's (EPA) Air Quality System (AQS). When AQS data are available from multiple monitors for a given county and day, the highest 24-h average (daily) PM2.5 concentration among all the monitors is selected for purposes of creating daily county level data. EPA provides modeled estimates of PM2.5 using Downscaler (DS) model, which uses a statistical approach to fuse monitoring data in areas where monitors exist, and relies on Community Multiscale Air Quality (CMAQ) modeled output in areas without monitors. DS modeled estimates are available by census tract centroid-the geographic center of the census tract. Daily county-level modeled estimates are obtained by selecting the maximum value observed among all the census tracts within each county. County-level PM2.5 measures are created using monitor data when available and using modeled estimates for days and locations without such data. The model is intended to model the level of pollutants in the layer of atmosphere that we are breathing as we assume that the pollutants are equally distributed across the county.While this measure estimates the average annual concentration of fine particulate pollution in the county, it can miss important short-term fluctuations in air quality (such as stagnation events), local patterns (high concentrations near roads and other major sources), and other pollutants (such as ozone, etc.).

Drinking Water Violations has only two values: Yes and No. A “Yes” indicates that at least one community water system in the county received at least one health-based violation during the specified time frame. A “No” indicates that there were no health-based drinking water violations in any community drinking water system in the county. Health-based violations include Maximum Contaminant Level, Maximum Residual Disinfectant Level, and Treatment Technique violations.

Severe Housing Problems is the percentage of households with one or more of the following housing problems:

• Housing unit lacks complete kitchen facilities;
• Housing unit lacks complete plumbing facilities;
• Household is overcrowded;
• Household is severely cost burdened.

Driving Alone to Work is the percentage of the workforce that usually drives alone to work. The numerator is the number of workers who commute alone to work via car, truck, or van. The denominator is the total workforce.

Long Commute - Driving Alone is the percentage of workers who drive alone with a commute longer than 30 minutes. The numerator is the number of workers who drive alone (via car, truck, or van) for more than 30 minutes during their commute. The denominator is the number of workers who drive alone (via car, truck, or van) during their commute.