Disinfection byproducts
Perchlorate in U.S. tap water
233 public water systems across 8 U.S. states report Perchlorate in their annual Consumer Confidence Report. None currently sit at or above the federal limit.
What it is
A chemical used in rocket fuel and fireworks that can also form during disinfection.
Why it's regulated
Can interfere with thyroid hormone production; has no national enforceable limit but is regulated in some states.
Within the federal limit (47)
Perchlorate by state
Every state where a public water system reports Perchlorate in its annual report, ranked by systems at or above the federal limit.
Frequently asked
+What is Perchlorate?
A chemical used in rocket fuel and fireworks that can also form during disinfection. Can interfere with thyroid hormone production; has no national enforceable limit but is regulated in some states.
+What is the federal limit for Perchlorate in drinking water?
The federal Public health goal for Perchlorate is 1 ug/L. The EPA enforces this against the regulated reporting statistic (typically a running annual average or 90th percentile), not a single-sample spike.
+How many U.S. water systems have Perchlorate over the federal limit?
Zero of the 233 public water systems in The Water Map dataset currently report Perchlorate at or above its federal limit.
+Which states report the most Perchlorate in their drinking water?
No state currently has a system reporting Perchlorate at or above its federal limit in The Water Map dataset. California, Wisconsin, Massachusetts have the most systems measuring it.
+How can I check if Perchlorate is in my city's tap water?
Search your city on The Water Map (https://www.thewatermap.com/) or browse the list on this page. Every U.S. public water utility is required to publish an annual Consumer Confidence Report that lists every contaminant it measured, including Perchlorate.