Radioisotopes are used as tracers in many research areas. Most physical, chemical and biological systems treat radioactive and non-radioactive forms of an element in exactly the same way, so a system can be investigated with the assurance that the method used for investigation does not itself affect the system. An extensive range of organic chemicals can be produced with a particular atom or atoms in their structure replaced with an appropriate radioactive equivalent.
Using tracing techniques, research is conducted with various radioisotopes which occur broadly in the environment, to examine the impact of human activities. The age of water obtained from underground bores can be estimated from the level of naturally occurring radioisotopes in the water. This information can indicate if groundwater is being used faster than the rate of replenishment. Trace levels of radioactive fallout from nuclear weapons testing in the 1950s and 60s is now being used to measure soil movement and degradation. This is assuming greater importance in environmental studies of the impact of agriculture.