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Nitrate at Cwsc King City

California · system CA2710009 · serves 16,334 people

Band placed by this system's most recent reported result within a rolling three-year window; the three-year range below shows the full spread.

The reading

5.20 mg/L as N
most recent reading · Aug 2024
1.1 to 5.5
three-year range (mg/L as N)
31 samples
what this result rests on
16,334
people served

A single reading is not a complete account of what a household drinks, so the three-year range and the number of tests behind it are shown too — a reading backed by many tests over three years is a fuller picture than one from a single sample.

Source: California State Water Resources Control Board - Division of Drinking Water drinking-water records (bulk data feed; no per-record link) · California · system CA2710009 · the three years from August 9, 2023 to August 9, 2026

Where this ranks

This system's nitrate sits in the top 6% nationally. Systems reporting less serve about 94% of everyone on NitrateSmart's tracked supply; the other about 6% are on systems reporting the same or more. That compares what systems reported, not what comes out of any one tap.

Natural backgroundHuman impact likelyHuman impact clearHealth-study rangeAbove the federal limit

What "Health-study range" means

Two long-term studies of Iowa women reported higher cancer rates among people whose drinking water stayed above 5 mg/L as N for years[1][2] — thyroid cancer where the supply ran above that level for more than five years, bladder cancer where it did for four years or more — still below the federal limit of 10. Both are observational: they find associations, not proven cause, and the difference for any one person is small. In both, concentration alone fell short of significance and the years spent above 5 reached it, so 5 mg/L as N is a level that matters when it persists. Associations are also reported at lower levels; this band marks the level those two studies used. Whether this system has held this level for years is not something the three-year window below can show, and this page does not claim it.

If there is a pregnancy or an infant under about six months in the household, this is the circumstance the research concentrates on. It is worth a conversation with a clinician, who can weigh this number against everything else.

Sources

  1. Ward, M.H., and others (2010). Nitrate intake and the risk of thyroid cancer and thyroid disease. Epidemiology 21(3):389–395. Thyroid cancer, more than five years on public supply above 5 mg/L nitrate-N: RR 2.59 (1.09–6.19), 8 exposed cases. Exposure reported as nitrate-N.
  2. Jones, R.R., and others (2016). Nitrate from drinking water and diet and bladder cancer among postmenopausal women in Iowa. Environmental Health Perspectives 124(11):1751–1758. Bladder cancer, four or more years above 5 mg/L NO3-N: HR 1.62 (1.06–2.47), 29 cases. Exposure reported as NO3-N.

The bands describe how strongly human activity, read from nitrate, has marked a water source — they are not a safety verdict. More on what the numbers mean and where nitrate comes from.

From here

Nitrate across California
How this system sits among the state's others, and the California story.
What actually removes nitrate
Which home treatments work, which don't, and the one that makes it worse.
NitrateSmart

Nitrate in community water systems, from the utilities’ own compliance reporting.

Results reaching back to July 2023 · current through August 9, 2026.

Data & methods

How this is built
Coverage and gaps

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Educational information, not medical or personal safety advice.