Routine testing in Largo, Florida turned up Arsenic — samples from the public supply came back positive, placing this contaminant on the list of substances residents here have a concrete reason to look into.

Data: EPA SDWIS, CCR Reports, ECHO Last verified: 2026-04-05

Arsenic in Largo Tap Water

Arsenic has been detected in Largo, Florida drinking water at a maximum level of 400 ppb — 40x the EPA MCL.

This analysis covers 105,903 residents across 6 ZIP codes in Largo.

Largo's overall water quality grade is B (72/100).

Is Arsenic in Largo 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

Average arsenic level across Largo: 400 ppb

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 Largo Water

1. Install a reverse osmosis (RO) system certified under NSF 58
2. Adsorptive media filters (iron-based) can also reduce arsenic
3. Have well water tested if on a private supply
4. Boiling water does NOT remove arsenic — it concentrates it

Look for filters certified under NSF 53 / NSF 58 for arsenic removal.

Related

• Arsenic — National Overview
• Florida Water Quality
• Largo Water Quality
• Check Your ZIP Code