Background and Objectives
Agrochemicals are an important agricultural input to protect crops from diseases, pests and weeds. Use of agrochemicals contributes not only to healthy growth of crops but also to improved farm work efficiency and stable supply of tasty agricultural produce.
But concerns are raised about the possibility that the agrochemicals used in farmland can spread out into the adjacent environment or persist in the ecosystem and may have an adverse impact on crops as well as on people and the environment. Apart from agrochemicals, there are organic chemical substances that are known as “persistent organic pollutants (POPs).” POPs resist degradation in the environment, are prone to accumulate in living bodies, and tend to travel long distances. Accordingly, they are considered to present a high risk of adverse impact on humans, animals and the environment.
In nature, there are many living creatures. While the number of species and their respective populations change according to the season and the weather, the so-called “biodiversity” is maintained. Is this biodiversity adversely affected by agrochemicals, POPs and other organic chemicals, and if so, what are the solutions? These are the questions we are pursuing in our research.
With the aim of assessing the impact of agrochemicals and POPs upon the environment, the following research projects are underway:
- (1) Exposure assessment: Computer simulation models will be developed and made available to the public with respect to the behavior of agrochemicals and POPs in the environment, particularly in rice paddies, the major agricultural setting in Japan and in all of Asia. How POPs diminish in the environment will be elucidated.
- (2) Toxicity assessment: Long-term impact of agrochemicals and other substances on algae, insects and other aquatic life living in rivers downstream of rice paddies will be analyzed. In addition, methodologies for risk assessment that integrate the exposure assessment and toxicity assessment will be developed.
- (3) Risk reduction technologies: Technologies utilizing microorganisms and plants to clean up the soil contaminated by Drin insecticides and other POPs will be developed. In so doing, the combined use of surfactants, activated carbon or other chemical materials will be pursued.
Fig. 1 Research flow in the development of environmental risk assessment methodologies and risk reduction technologies for agrochemicals and other substance
Fig. 2 Examples of persistent organic pollutants (POPs)
Relevant Outcomes to Date
- (1) Exposure assessment: A simulation model for agrochemicals concentration in rice paddies and rivers has been proposed (Fig. 3), serving as the prototype for models to predict global behavior of POPs and other chemicals. In addition, the half-life of dioxins in soil (the time period during which the concentration is reduced by half) has been estimated.
- (2) Toxicity assessment: The work to prepare a manual on the test methods of agrochemicals acute toxicity to common species of algae in rivers is almost complete (Fig. 4). In addition, a method to rear caddis fly, an important index organism for aquatic insects, has been developed successfully.
- (3) Risk reduction technologies: Differences in Drin pesticides absorption among plant varieties have been elucidated. A basic technology to decompose agrochemicals has been developed through the retention of a variety of bacteria in charcoal (Fig. 5).
Fig. 3 Simulation model for agrochemicals concentration in rivers
Fig. 4 Acute toxicity test of agrochemicals to algae
Fig. 5 Bacteria are retained in charcoal to decompose agrochemicals