Biodegradability

Bacteria and fungi use many organic chemicals as food. Standard laboratory screening tests measure how much of a substance is consumed over a set time under controlled conditions. A chemical that passes a stringent screening test is described as readily biodegradable, while others may be inherently biodegradable, meaning they can break down but more slowly or under favorable conditions.

Biodegradable does not mean harmless. A chemical can be broken down by microbes yet be toxic to fish or algae while it is still present. Breakdown may also take time and produce intermediate products, so a release can cause damage before it disappears. Biodegradability and toxicity are separate questions.

The term also gets stretched in marketing. A label saying biodegradable is not a regulatory category in the same way as hazard classification, and the conditions behind the claim, such as industrial composting, may not exist in a drain or waterway. The SDS is more precise: it normally reports test method and result.

Inorganic substances like metals and many salts do not biodegrade, since they are elements and cannot be consumed. For these the SDS normally states that the test does not apply, and persistence is described in another way.