DES MOINES – Iowa’s lakes and beaches are summer hotspots, but staying safe means staying informed. The Iowa Department of Natural Resources (DNR) tests beach water weekly from Memorial Day to Labor Day, monitoring E. coli and microcystins to ensure safe swimming conditions.

What’s Tested?

• E. coli: Bacteria indicating potential pathogens. High levels may cause minor illnesses like diarrhea or nausea.

• Microcystins: Toxins from cyanobacteria (blue-green algae). Only 2-7% of 2024 tests triggered warnings, affecting seven beaches.

When Are Advisories Issued? Advisories are posted when:

• E. coli exceeds 126 CFU/100mL (geometric mean) or 235 CFU/100mL (single sample).

• Microcystins exceed 8 µg/L.

Advisories signal caution, not closure. Avoid swimming if you might swallow water, especially with young kids or weakened immune systems. Stay clear of algae-heavy areas resembling oily paint.

How Risky Is It? At 235 CFU/100mL, about 36 per 1,000 swimmers may experience minor illness. Risks rise with higher levels or water ingestion.

Beyond Water Quality: Drowning Risks Most beach injuries and fatalities stem from drowning. Watch children closely, know your swimming limits, and wear lifejackets. Cold spring water can increase drowning risk by lowering body temperature.

Stay Safe, Enjoy Iowa’s Lakes Check DNR advisories, avoid algae, and follow safety guidelines to enjoy Iowa’s lakes confidently. For more, visit iowadnr.gov.