Each location card lists every other-health-risk pollutant measured at that site, the health effects each one is associated with, and its risk over time — the average concentration divided by the screening level. A value below 1.00x is below the screening level; 1.00x is the screening level itself. The bottom Total row adds those ratios across all pollutants at that site, the same “Total” definition used on the main dashboard.
CHATTER analyzes air pollutants measured with automatic gas chromatograph (AutoGC) equipment. In Houston, CHATTER follows all fourteen hourly AutoGC monitors in Harris County — Clinton, Manchester East Avenue N, Houston Milby Park and Cesar Chavez (East End); Galena Park and Pasadena Richey Elementary School (Galena Park / Pasadena); HRM-3 Haden Road (Jacinto City / Cloverleaf); Channelview, Channelview Drive Water Tower and Lynchburg Ferry (Channelview / Lynchburg); HRM-16 Deer Park and Houston Deer Park #2 (Deer Park); and Wallisville Road and HRM-7 W Baytown (Baytown) — grouped into the six sections of the monitor map. Each section below is a tabbed card: click a monitor’s name to see its heatmap. Hatched gray cells mean no measurement exists for that pollutant in that period.
How to read this plot (click to expand)
Each row is an air pollutant, with the health system or target organ it is associated with listed beside it. Each column is a period of time. The bottom row, Total, adds all the pollutants together for that period. The number in each square is the measured level divided by the EPA screening level, written as a multiple with an “x.”
A clarifying example.In the Galena Park / Pasadena section, open the Galena Park tab and find the row for Benzene and the column for 2024. The square reads 0.090x. The health effect listed beside benzene is Immune system, meaning breathing benzene at high enough levels can affect the immune system. The number means the average benzene level in 2024 was about 9% of the screening level — well below it. In the same column, the Total row reads 0.405x: adding all thirteen pollutants together, the combined level was about 40% of the screening level.
Most of this tab is below the screening level. The color scale does not begin to darken until 0.75x, and almost every value sits far under that, so most of the grid appears in the palest shade. That is the finding, not a rendering problem. The exception is 1,3-butadiene at Houston Milby Park (East End section), which exceeds the screening level in several periods and lifts that site’s Total above 1.0x. Read the numbers to compare pollutants, sites, and years.
Hatched gray squares mean the pollutant was not measured in that period — which is different from a low reading, and so is marked differently.
For a general explanation of heat maps, see the Frequently Asked Questions.
