Denial of writ of mandate is reversed and defendant is ordered to complete an assessment on the public health impacts of the rule 4570, which requires large confined animal facilities to choose from a variety of mitigation measures with the goal of reducing VOC emissions, where: 1) rule 4570 was adopted without conducting an adequate assessment of its impact on public health, as mandated by Health and Safety Code section 40724.6; 2) section 40724.6 was intended to address the district's failure to meet federal and state ambient air quality standards for ozone and does not regulate ammonia emissions produced by large confined animal facilities; and 3) the district's findings were not arbitrary and capricious.