Atrazine is one of the most studied molecules in history. More than 7,000 studies attest to its safety, which is why the EPA has repeatedly reapproved its use after extensive, successive reviews as part of the ongoing re-registration process. In 2011, after reviewing the latest safety data, the World Health Organization raised its recommended atrazine limit in drinking water from 2 to 100 parts per billion. In the U.S., the limit remains much lower — at 3 parts per billion, though the Office of Pesticide Programs has calculated it could safely be set 193 times higher at 580 parts per billion. Australian regulators decided in 2008 to maintain their standard at 40 ppb. The fact is, a 150-pound adult could drink hundreds of gallons of water containing the EPA limit of 3 ppb atrazine every day for 70 years and would still not reach a level of exposure shown to have any effect in laboratory studies.
The Syngenta/EPA Atrazine Monitoring Program (AMP) monitored at-risk community water systems on a weekly basis. This program continually proved that the state-run quarterly Safe Drinking Water Act monitoring program protected human health through quarterly sampling. When the weekly monitoring data was averaged over a year, no human health thresholds were ever exceeded. From 2004-2019, the program demonstrated the safety of drinking water in the most vulnerable drinking water systems and also determined that the Safe Drinking Water Act was protective for the 3ppb Maximum Containment Level (MCL). For this reason, the U.S. EPA allowed the discontinuation of the AMP. Drinking water is still protected and monitored by the state-run quarterly Safe Drinking Water Act monitoring program. Additionally, all community water systems (CWS) are monitored for atrazine levels under the Safe Drinking Water Act. Results of that program are annually reported to EPA and the CWS also report local results to consumers of the drinking water.
The Atrazine ecological exposure monitoring program was started in 2004 to monitor atrazine levels in watersheds across the United States. It is the most robust monitoring program for atrazine ever carried out. It includes daily sampling data throughout the atrazine use season. On October 22, 2019, EPA issued an Atrazine Regulatory Update (October 2019) that re-evaluated and raised the concentration equivalent level of concern (CE-LOC) used to assess atrazine’s potential effects on aquatic plant communities from 10 µg/L to 15 µg/L. EPA reconfirmed the CE-LOC of 15 µg/L in its Atrazine Proposed Interim Registration Decision (December 2019) and Atrazine Interim Registration Decision (September 2020).