Basic Knowlegde of Agricultural Chemicals
5. Evaluation for environmental safety
In addition to safety to humans and livestock, the safety to aquatic organisms, honeybees and other rodents is inspected for registration of agricultural chemicals.
(1) Effects on aquatic organisms
Uniform standards for withholding registration are established for aquatic organisms, on the basis of 48-hour lethal concentration of 50% of the common carp (LC50). The test organisms were limited to common carp, and the exposure in the environment was not considered in the calculation, which require further investigation.
This led the Ministry of the Environment to revise the Notification of the Ministry of the Environment, in which it is stated that the evaluation methods for safety shall be modified, in which the toxicity values to fish, crustacea, and algae, and the predicted concentration of agricultural chemicals in public water areas shall also be included in the evaluation studies for comparison. This is to prevent adverse effects of agricultural chemicals on wildlife and ecosystems, and enhance the efforts to enforce the standards for withholding registration concerning toxicity to aquatic organisms, with a view to maintaining the natural ecology. This revision was put into effect in April 2005.
The Ministry of Agriculture, Forestry and Fisheries requires study results in which daphnids are tested as crustacea, and a kind of phytoplankton is tested as algae, in addition to the common carp as fish. In fish toxicity tests, 96-hour median lethal concentration (LC50) shall be obtained, and in daphnids Immobilization tests, 48-hour median effective concentration (EC50) shall be obtained to determine the degree of effects, which will be reflected in the precautions for use of agricultural chemicals.
(2) Effects on beneficial insects
Studies in various beneficial insects (e.g., silkworms, honeybees, and natural enemies) are conducted to investigate the effects on these insects. The median lethal dose (LD 50) in honeybees, and the residual toxicity period in silkworms were investigated to establish safe handling measures when using agricultural chemicals.
(3) Effects on avians
Studies on the effects on avians are conducted as needed, considering the site and the type of formulation to be sprayed. When acute oral toxicity studies in Japanese quails and mallard ducks reveal strong toxicity, avian dietary toxicity tests will also be conducted subsequently to investigate the effects on avians.
(4) Physical properties, stability, degradability, and others, of active ingredients
These studies are conducted to obtain essential and basic scientific information concerning the safety evaluations, including the physical properties, stability, and degradability of active ingredients and other components of agricultural chemicals. The study results also serve as an important index for estimating the environmental pharmacokinetics.
