Air monitoring studies conducted by the California Air Resources Board (CARB) documented chlorpyrifos in the air of California communities. Analyses indicate that children living in areas of high chlorpyrifos use are often exposed to levels that exceed EPA dosages. A study done in Washington state using passive air samplers showed that households who lived less than 250 meters from a fruit tree field had higher levels of chlorpyrifos concentrations in the air than households that were further away. Advocacy groups monitored air samples in Washington and Lindsay, California, in 2006 with comparable results. Grower and pesticide industry groups argued that the air levels documented in these studies are not high enough to cause significant exposure or adverse effects. A follow-up biomonitoring study in Lindsay also showed that people there display above-normal chlorpyrifos levels.