FRESNO -- Bans on burning wood in fireplaces have plummeted more than 50 percent in the San Joaquin Valley -- the benefit of better air movement compared to the stagnant winter of 2011-12.
But on 42 days this winter, the air still violated the federal particle pollution standard somewhere in the valley, according to the California Air Resources Board.
Residents in the eight-county region, ranging from Stockton to Bakersfield, are cooperating when burning bans are called, according to the San Joaquin Valley Air Pollution Control District. Citations for violating the wood-burning ban dropped more than 50 percent.
"Valley residents have come to understand the serious health consequences of residential wood burning and support this critical regulation," district executive director Seyed Sadredin said. "Our improving winter air quality reflects that."
Wood-burning bans ended this week for the season, which runs from November through February.
Soot, diesel particles, chemicals and other microscopic specks called PM-2.5 are linked to asthma, heart problems and the early death of hundreds of valley residents each year.
Wood burning in cities is one of the valley's biggest PM-2.5 problems -- which rank among the worst in the country.
A decade ago, the district passed a rule curtailing wood burning when air quality deteriorates. It prevents buildups of the specks. Since then, violations, pollution concentrations and unhealthy days have dropped.
But this region is a natural trap for pollution because of surrounding mountains and episodes of stagnant weather. In the dry, cold month of December 2011, for instance, there were 29 consecutive days when PM-2.5 exceeded the federal standard somewhere in the valley.
In the last four months, Fresno and Kern counties had the most bans on wood burning, as they did in the previous winter. Fresno County had 43 this season, 68 last. Kern had 36 this season, 56 last.
Overall in the valley, there were 187 bans this winter, 381 last year.