Through various programs and in cooperation with State air, environmental or health agencies, EPA requires monitoring for criteria air pollutants. Through these monitoring programs, air quality samples are collected to judge attainment of the air quality standards, to aid in preventing or alleviating air pollution emergencies, and to observe pollution trends throughout regions. These programs monitor all of the criteria pollutants. Measurements are taken to assess areas where there may be a problem, and to monitor areas that already have problems. The goal of these monitoring program is to inform areas of where problems exist and to provide information that will enable areas to prevent future air quality problems.