Health

Health Risks

How dangerous are cyanobacteria?

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In Emergency

For severe symptoms or if you swallowed larger amounts of contaminated water:

📞 Poison Control: 030 19240🚑 Emergency: 112

🎯Exposure Routes

How cyanotoxins enter the body

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Ingestion

Highest risk while swimming (especially children) or contaminated drinking water

Highest Risk

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Skin Contact

Direct contact with contaminated water, algae foam or sediment

Medium Risk

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Inhalation

Aerosol formation during water sports or near intense blooms

Lower Risk

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Food Chain

Consumption of contaminated fish, shellfish or plant products

Accumulation Risk

🩺Symptoms by Organ System

Symptoms vary depending on toxin type and exposure route

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Skin

•Itching, redness
•Rash, blisters
•Eye burning on contact

Onset: Minutes to hoursSeverity: Mild

🤢

Gastrointestinal

•Nausea, vomiting
•Diarrhea, abdominal cramps
•Loss of appetite

Onset: Hours to daysSeverity: Moderate

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Respiratory

•Cough, throat irritation
•Shortness of breath, tightness
•Asthma-like symptoms

Onset: Minutes to hoursSeverity: Moderate-Severe

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Nervous System

•Headache, dizziness
•Tingling, numbness
•Muscle cramps, tremors

Onset: MinutesSeverity: Severe

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Liver

•Jaundice
•Elevated liver enzymes
•Right-sided pain

Onset: Days to weeksSeverity: Severe

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General

•Fever, chills
•Fatigue, weakness
•Flu-like symptoms

Onset: Hours to daysSeverity: Mild-Moderate

⚠️High-Risk Groups

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Young Children

Drink more water per body weight, play in water

💡 Extra caution when swimming, no swallowing

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Immunocompromised

Body less able to break down toxins, more susceptible to infections

💡 Avoid contact with suspicious water

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Pregnant Women

Toxins can harm the fetus, especially certain neurotoxins

💡 Avoid swimming entirely during warnings

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Dogs

Drink lake water, lick their fur, small body size

💡 Highest danger! Deaths possible within minutes

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Asthmatics

Inhaling aerosols can trigger attacks

💡 Keep distance from blooms, avoid spray

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Elderly

Often pre-existing conditions, slower metabolism

💡 See a doctor early if symptoms appear

📈Long-term Effects

Long-term effects of cyanotoxin exposure are not yet fully understood, but there are concerning indications:

⚠️IARC Classification:

Microcystin-LR is classified by IARC as "possibly carcinogenic to humans" (Group 2B).

Cancer Risk

Studies in China show increased liver cancer rates in regions with cyanobacteria-contaminated drinking water

Neurological Effects

BMAA is linked to neurodegenerative diseases (ALS, Alzheimer's, Parkinson's)

Chronic Damage

Repeated exposure can lead to permanent liver and kidney damage

Most findings on long-term effects come from animal studies or individual poisoning cases. Epidemiological long-term studies in humans are rare.

📋Official Guidelines

WHO Risk Levels for Recreational Waters

Low Risk

<20,000 cells/mL, <10 µg/L MC-LR

Swimming permitted

Moderate Risk

20,000-100,000 cells/mL, 10-20 µg/L MC-LR

Caution advised

Elevated Risk

>100,000 cells/mL, >20 µg/L MC-LR

Limit swimming

High Risk

Visible blooms, algae foam, >2mm depth visibility reduction due to algae

Swimming prohibited

Source: WHO (2021). Guidelines on recreational water quality. Volume 1: Coastal and fresh waters.

📚 Sources & References

[1] IARC (2010). Ingested nitrate and nitrite, and cyanobacterial peptide toxins. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 94.

[2] Falconer, I. R. (1999). An overview of problems caused by toxic blue–green algae (cyanobacteria) in drinking and recreational water. Environmental Toxicology, 14(1), 5-12.

[3] Cox, P. A. et al. (2016). Diverse taxa of cyanobacteria produce β-N-methylamino-L-alanine, a neurotoxic amino acid. PNAS, 102(14), 5074-5078.

[4] WHO (2021). Guidelines on recreational water quality. Volume 1: Coastal and fresh waters.

[5] EPA (2019). Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin.