Radionuclides
Gross Alpha in U.S. tap water
849 public water systems across 32 U.S. states report Gross Alpha in their annual Consumer Confidence Report. 18 sit at or above the federal limit.
What it is
Gross alpha particle activity — a combined measure of alpha-emitting radioactive substances.
Why it's regulated
Long-term exposure above the federal limit increases cancer risk.
At or above the federal limit (18)
| Water system | Measured | vs. limit |
|---|---|---|
| Philadelphia, PA 2023 annual report | 228 pCi/L | 15.2× the limit |
| Crestline Village Cwd - Division 10 — Crestline, Ca, CA 2023 annual report | 37–93 pCi/L | 6.2× the limit |
| Indian Hills Camp — Jamul, Ca, CA 2023 annual report | 0–77 pCi/L | 5.1× the limit |
| St Petersburg, FL 2024 annual report | 0–40 pCi/L | 2.7× the limit |
| Pine Valley Mutual Wc — Pine Valley, Ca, CA 2023 annual report | 14.9–35.7 pCi/L | 2.4× the limit |
| Cal Am - Bass Lake — Sacramento, Ca, CA 2023 annual report | 23.8 pCi/L | 1.6× the limit |
| Yosemite Spring Park Util Co — Coarsegold, Ca, CA 2023 annual report | 1.67–23.5 pCi/L | 1.6× the limit |
| Valley of Enchantment Mwc — Crestline, Ca, CA 2023 annual report | 0–22.5 pCi/L | 1.5× the limit |
| Poolesville, MD 2024 annual report | 22.4 pCi/L | 1.5× the limit |
| Camp Pendleton (north) — Camp Pendleton, Ca, CA 2023 annual report | 0–21.7 pCi/L | 1.4× the limit |
| Camp Pendleton (south) — Camp Pendleton, Ca, CA 2023 annual report | 0–21.7 pCi/L | 1.4× the limit |
| San Miguel Community Services District — San Miguel, Ca, CA 2023 annual report | 10.8–18 pCi/L | 1.2× the limit |
| Desert Water Agency — Palm Springs, Ca, CA 2023 annual report | 1.3–17 pCi/L | 1.1× the limit |
| Burbank, CA 2024 annual report | 0–16.9 pCi/L | 1.1× the limit |
| Nampa, ID 2024 annual report | 16 pCi/L | 1.1× the limit |
| Elsinore Valley MWD — Lake Elsinore, Ca, CA 2022 annual report | 11.6–15.5 pCi/L | 1.0× the limit |
| Home Gardens County Wd — Corona, Ca, CA 2022 annual report | 0–15 pCi/L | 1.0× the limit |
| Malaga County Water District — Fresno, Ca, CA 2021 annual report | 1.4–15 pCi/L | 1.0× the limit |
Approaching the limit (16)
| Water system | Measured | vs. limit |
|---|---|---|
| Lakeside Park Association — South Lake Tahoe, Ca, CA 2023 annual report | 14.7 pCi/L | 1.0× the limit |
| Bear Valley Csd — Tehachapi, Ca, CA 2022 annual report | 14.15 pCi/L | 0.9× the limit |
| City of South Pasadena — South Pasadena, Ca, CA 2022 annual report | 0–14 pCi/L | 0.9× the limit |
| City of South Pasadena — South Pasadena, Ca, CA 2023 annual report | 0–14 pCi/L | 0.9× the limit |
| Kerman, City of — Kerman, Ca, CA 2023 annual report | 14 pCi/L | 0.9× the limit |
| Rochester, MN 2025 annual report | 14 pCi/L | 0.9× the limit |
| Frazier Park Pud — Frazier Park, Ca, CA 2022 annual report | 13.9 pCi/L | 0.9× the limit |
| Pleasant Valley Mutual Water Co — Camarillo, Ca, CA 2023 annual report | 1.74–13.3 pCi/L | 0.9× the limit |
| San Joaquin, City of — San Joaquin, Ca, CA 2023 annual report | 0–13.2 pCi/L | 0.9× the limit |
| Bighorn - Desert View Water Agency — Yucca Valley, Ca, CA 2023 annual report | 13 pCi/L | 0.9× the limit |
| Palmdale Water Dist. — Palmdale, Ca, CA 2023 annual report | 13 pCi/L | 0.9× the limit |
| Hi Desert Wd — Yucca Valley, Ca, CA 2023 annual report | 3.12–12.8 pCi/L | 0.9× the limit |
| Fillmore Water Dept — Fillmore, Ca, CA 2023 annual report | 3.18–12.6 pCi/L | 0.8× the limit |
| Yuma, AZ 2025 annual report | 12.5 pCi/L | 0.8× the limit |
| Solvang Water Division — Solvang, Ca, CA 2023 annual report | 1.51–12.4 pCi/L | 0.8× the limit |
| Clarksville, TN 2024 annual report | 12 pCi/L | 0.8× the limit |
Within the federal limit (815)
Showing 50 of 815. The full list is in the JSON API.
Frequently asked
+What is Gross Alpha?
Gross alpha particle activity — a combined measure of alpha-emitting radioactive substances. Long-term exposure above the federal limit increases cancer risk.
+What is the federal limit for Gross Alpha in drinking water?
The federal MCLG for Gross Alpha is 0 pCi/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 Gross Alpha over the federal limit?
18 of the 849 public water systems on The Water Map report Gross Alpha at or above its federal limit, spanning 32 U.S. states. The full list is on this page.
+How can I check if Gross Alpha 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 Gross Alpha.