Toxic elements are primarily released into the environment by industrial activity, although ground source levels can also be significant in some areas. Their use is widespread leading to many possible sources of exposure along with contamination in the food chain (i.e. fish and rice in particular). Toxic elements serve no biochemical purpose, and human biochemistry is adversely affected by exposure (which can impair biochemical pathways and result in accumulation with time). Exposure to, and in some cases accumulation of, toxic elements has been associated with many of the health problems commonly seen in Western populations.