US Water Score: A
| Contaminant | Detected Level | EPA MCL | Health Guideline | Status |
|---|---|---|---|---|
| Lead |
10.75
|
15 ppb | 1 ppb | Warning |
UCMR5 occurrence results are screening information, not a finding of regulatory compliance or noncompliance. PFAS rules and compliance dates are evolving.
| Compound | Level | EPA MCL | Health Guideline | Status |
|---|---|---|---|---|
| PFOS | 19.0 ppt | 4 ppt | 4 ppt | Above comparison value |
| PFHxS | 11.0 ppt | 10 ppt | 10 ppt | Above comparison value |
| PFOA | 8.5 ppt | 4 ppt | 4 ppt | Above comparison value |
| PFBA | 5.7 ppt | No standard | 500 ppt | No federal MCL shown |
| PFBS | 3.5 ppt | 2000 ppt | 100 ppt | Below comparison value |
| PFPeA | 3.5 ppt | No standard | — | No federal MCL shown |
| PFHxA | 3.1 ppt | No standard | 400 ppt | No federal MCL shown |
Water Quality Summary
Tap water quality in Altadena, California (91001) receives an overall grade of A (Lower record-based concern) with a score of 99 out of 100, based on analysis of EPA compliance data, contaminant testing, and violation history. This is 6 points above the California state average of 92. Compared to the national average (75), this area performs significantly better. The area is served by 5 water systems providing water to approximately 164,344 people, using surface water and groundwater sources. Testing has found elevated levels of Lead that warrant attention. Notably, 3 PFAS compounds exceed the EPA final MCL value used for comparison — a significant concern given the persistent nature of these chemicals. The area has a clean violation record over the past 5 years — a positive indicator of consistent water quality management.
A score of 99/100 means public water-system records for Altadena, CA show relatively few concerns in the US Water Score model. This is an internal score, not an EPA safety rating, and it does not guarantee conditions at any specific tap.
Health Information
Lead is a toxic metal that can leach from aging pipes and plumbing fixtures.
Even low levels of lead exposure can cause developmental delays in children, kidney damage, and cardiovascular effects in adults. The EPA action level is 15 ppb, but health experts recommend no safe level of lead in drinking water.
Lead enters water primarily through corrosion of lead service lines, lead solder, and brass fixtures — especially in homes built before 1986.
If lead is detected above 1 ppb, consider using a certified lead-removal filter (NSF/ANSI 53) for drinking and cooking water. Run cold water for 30 seconds before use if water has been sitting in pipes.
Common Questions
Based on public water-system records, Altadena, California receives an internal US Water Score grade of A (Lower record-based concern) with a score of 99/100. This indicates relatively few system-level concerns in our model, but it is not an EPA safety rating and does not guarantee tap conditions inside individual homes.
ZIP code 91001 is served by 5 water systems using surface water, groundwater sources, providing water to approximately 164,344 people. Multiple source types mean your water may come from a blend of surface and underground sources.
Lead was reported at 10.75 ppb in public-system records for Altadena, California. This is below the currently applicable EPA action level of 15 ppb, but may be above more protective health guidance; EPA's future LCRI action level is 10 ppb. Household plumbing can materially change tap-level exposure, so consider certified filtration and individual tap testing, especially where children are present.
Yes — 7 PFAS compounds were detected in records associated with water serving Altadena, California, and 3 results exceeded the numerical EPA MCL value used for comparison. UCMR5 occurrence results alone are not a regulatory compliance determination. PFAS rules and compliance timelines are evolving; verify current information with the utility and EPA.
Water systems serving Altadena, California have zero violations in the last 5 years. This is a positive indicator of consistent regulatory compliance and water quality management.
Based on detected contaminants (lead, PFAS), residents in Altadena, California should consider: Reverse osmosis (RO) system — most effective for PFAS, lead, and other contaminants. Always look for filters with NSF/ANSI certification for the specific contaminants you want to remove.
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