Arsenic in Hollister, CA Drinking Water
Arsenic data for Hollister, California · 52,365 residents · 2 ZIP codes
Not every city shows Arsenic in its water data; in Hollister, California, federal sampling has confirmed its presence at detectable levels in at least one recent reporting cycle.
Data: EPA SDWIS, CCR Reports, ECHO Last verified: 2026-05-14
Arsenic in Hollister Tap Water
Arsenic has been detected in Hollister, California drinking water at a maximum level of 350 ppb — 35x the EPA MCL.
This analysis covers 52,365 residents across 2 ZIP codes in Hollister.
Hollister's overall water quality grade is C (64/100).
Is Arsenic in Hollister Water Safe?
If you live in an affected ZIP code, consider installing a reverse osmosis filter certified under NSF 53 / NSF 58 and testing your water independently.
Arsenic Levels by ZIP Code
| ZIP Code | Arsenic Level | EPA Limit | Status |
|---|---|---|---|
| 95023 | 350 ppb | 10 ppb | Exceeds limit |
| 95024 | 350 ppb | 10 ppb | Exceeds limit |
Average arsenic level across Hollister: 350 ppb
EPA Violations for Arsenic in Hollister
| Date | Violation Type | Status | ZIP Code |
|---|---|---|---|
| 2023-07-01 | Arsenic (Known) | Known | 95023 |
| 2023-07-01 | Arsenic (Known) | Known | 95024 |
| 2022-10-01 | Arsenic (Known) | Known | 95023 |
| 2022-10-01 | Arsenic (Known) | Known | 95024 |
Health Effects of Arsenic
- Increased risk of skin, bladder, lung, and kidney cancer
- Cardiovascular disease and type 2 diabetes
- Skin changes (darkening, thickening, lesions)
- Developmental effects in children exposed in utero
Health risk severity: High. Governed by the Arsenic Rule (2006).
How Arsenic Gets Into Drinking Water
- Natural deposits in rock and soil (especially in western U.S.)
- Runoff from orchards and glass/electronics production
- Historical use of arsenic-based pesticides
- Well water in areas with arsenic-rich geology
What to Do About Arsenic in Hollister Water
- Install a reverse osmosis (RO) system certified under NSF 58
- Adsorptive media filters (iron-based) can also reduce arsenic
- Have well water tested if on a private supply
- Boiling water does NOT remove arsenic — it concentrates it
Look for filters certified under NSF 53 / NSF 58 for arsenic removal.