题目内容：
阅读材料，回答题：Geology and Health
1The importance of particular metals in the human diet has been realized within the past fewdecades, and the ideathat geology might be related to health has been recognized for anumber ofelements such as iodine, zincand selenium. For example, soils with low iodine contents producecrops, and animals deficient in iodine. alack of iodine in the human diet leads to some seriousdiseases.
2The ultimate source of metals within the human body is rocks,which weather into soil, gainingor losing some of their chemical constituents. The crops we eat selectively remove from the soil theelements that they require for growth. The water we drink contains trace elements leached fromrock and soil. Thus the geology and geochemistry of the environments have effects on the chemis-try and health of plants,animals and people.
3So far there is no datato suggest that people living on metal-rich soils experience apotentialhealth hazard. The levels of metals within naturally contaminated soils are generally not highenough to cause serious health problems. Living on metal-rich soils does not represent ahealthrisk unless large quantities of soil are digested or metal-rich dust is inhaled. However, small chil-dren are particularly exposed to metal-rich topsoil in playgrounds and gardens. They are also themost likely ones to eat potentially dangerous metal-rich soil.
4Heavy metals are persistent: they do not break down to other chemicals in the environment.Industrially polluted sites usually undergo intensive clean-up and rehabilitation B．ecause heavymetals are ahealth concern once they enter the food chain. Some trace metals are alleged to causecancer and are also known to cause poisoning.
5In contrast,naturally contaminated soils have not been subject to risk assessment studies andrehabilitation measures, despite the fact that they frequently possess metal concentrations wellabove those of such polluted by humans and above environmental quality criteria.
6There is avital need to understand the potential risks and long-term health effects of living onnaturally contaminated soils. Future environmental investigations of naturally polluted soils shouldconcentrate on the potential pathways of metals into the food chain and human body. Geologist.,should be part of such studies as they can provide the essential background information on rocband soil chemistry as well as the chemical forms of heavy metal pollution.
Paragraph 1__________ A．No evidence to indicate bad effects of naturally contaminated soil
B．Potential hazards of human contaminated soils
C．Research on channels of heavy metals getting into human food chain
D．Geology and health problems
E．Rocks-the ultimate source of soil pollution
F．Long-term health effects on children
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