Phoslock is a modified bentonite clay product containing lanthanum, a naturally
occurring earth element. Several independent organizations have conducted extensive
laboratory and field studies on the toxicity of Phoslock using a range of aquatic
organisms and the United States Environmental Protection Agency toxicity testing
criteria. The results of acute and chronic toxicity tests of Phoslock and lanthanum
using a number of sensitive organisms including: several species of water flea (Daphnia);
several species of Rainbow fish; freshwater shrimp; benthic organisms such as amphipods,
mayflies and midge larvae; demonstrated no toxicity of Phoslock to aquatic organisms
at the dose rates used to remove FRP from surface waters.
The possibility of direct exposure of Phoslock and/or lanthanum to the human body
is very limited during or after an application of Phoslock. We suggest that there
is no risk to human health by a Phoslock application to a water body (including
drinking water reservoirs) at dose rates used to remove FRP from surface waters.
The safety margin is substantial and sufficient to ensure that the only exposure
of lanthanum (in Phoslock) would always be much less than the therapeutic dose used
in the medical industry. Handlers and applicators should always follow label and
The following reports summarizes Phoslock and lanthanum technical information, and a number of toxicity studies conducted by private and government agencies to assess the performance and potential risks associated with the use of Phoslock in natural aquatic environments.