July Ends With a Bang

Yet another ozone alert was issued today for the Denver metro area, marking the 26th ozone alert this month and the 40th so far this year. July 2007 has seen more ozone alerts than any July since at least 1999, if not earlier.

And with good reason. Following today's alert, ozone levels skyrocketed again. Eight hour ozone concentrations peaked at 94 parts per billion at the Rocky Flats monitor and exceeded 80 parts per billion in Boulder, Fort Collins, Arvada, Commerce City, and at Chatfield Reservoir. Current health standards limit ozone to no more than 80 parts per billion over an eight hour period.

We've already violated ozone standards in the Denver metro area, but is that violation just getting worse? It looks like that may be the case. Compliance with health standards is based on the three year average of the 4th highest ozone readings at each individual monitor. After today, the 4th highest readings for the year increased at 7 of the 12 Denver metro monitors.

The biggest jump was at the Chatfield monitor, where the 4th highest reading rose from 76 parts per billion to 80 parts per billion. If the 4th highest reading reaches 84 parts per billion, we'll have another violation of federal health standards on our hands.