Calcium oxide

Toxicity to birds

Description of key information

Information on this endpoint is required for the assessment of the risks for secondary poisoning. Secondary poisoning is concerned with toxic effects in the higher members of the food chain, either living in the aquatic or terrestrial environment, which result from ingestion of organisms from lower trophic levels that contain accumulated substances. In the environment, calcium oxide is transformed to calcium and hydroxyl ions and does not occur in its original form in living organisms. Therefore it is concluded that birds or other higher members of the food chain will not be exposed to calcium oxide as such and therefore this endpoint is considered not to be relevant. Furthermore, the levels of calcium and hydroxyl ions in organisms will be systemically regulated.
A large data set of studies is available on calcium carbonate, both laboratory studies using test animals and human data reported in the public domain. The toxicity profile of calcium carbonate in birds can therefore be predicted from that reported in the mammalian studies.
Calcium carbonate is naturally present in the environment and is a constituent of many foods. Comprising about 1.5% of a bird's weight, calcium is the predominant mineral in the body. It is therefore an essential element in a bird's diet and is used for bone formation, egg shell production and blood clotting. It also affects the heart, muscles and nerves, as well as some of the body's enzyme systems. Calcium carbonate is the main compound found in egg shells.
Based on the large mammalian dataset that is currently available and the ubiquitous nature of calcium carbonate in the environment, toxicity testing with birds is scientifically unjustified.