{{Toxicity}}
[[File:Biologisk korr.jpg|thumb|400px| Illustration: MiljöfarlighetsbedömningEnvironmental hazard]]
If a substance is '''toxic (toxicity)''' is determined by tests for various organisms. The most expensive but best method is to use fish as "guinea pigs". In other methods one can use water fleas or algae. Normally one investigates at what concentration of the substance half of the organisms die at. The trial period can be 48 hours.