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Lecture 6 : Environmental Factors (2) Overview

Lecture 6 : Environmental Factors (2) Overview. TRACE ELEMENTS WATER SUPPLY WATER POLLUTION DISCUSSION. Trace Elements. Some elements are essential for good health in trace quantities: Fe, I, F, Cu, Co, Mn, Cr, Mo, Se, Zn

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Lecture 6 : Environmental Factors (2) Overview

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  1. Lecture 6 : Environmental Factors (2) Overview • TRACE ELEMENTS • WATER SUPPLY • WATER POLLUTION • DISCUSSION

  2. Trace Elements • Some elements are essential for good health in trace quantities: Fe, I, F, Cu, Co, Mn, Cr, Mo, Se, Zn • Other elements can be dangerous, even in trace quantities: Hg, Pb, Cd,Be,Se, Zn • Some elements appear on both lists. Selenium, for example, is essential for health but is also 10,000 times more poisonous than Arsenic. • Trace elements in the underlying geology find their way into soils where they are taken up by plants. They may then be sonsumed by humans either as vegetables or through the meat of animals who ate the plants. • Given that our food now comes from a diversity of sources, the likelihood of a deficiency is probably slight.

  3. Water Supply • Water contains various elements in solution. Given that most people get most of their water from a single source, the water supply is a more likely source of a deficiency or excess. • Several studies suggest an association between soft water and heart disease. The soft water areas in Britain are associated with higher rates of heart disease. • The hard water areas in Britain also tend to be more affluent. However, the relationship between soft water and heart disease persists after controlling for social class. • Evidence from Scotland and Ireland cast some doubts on the hard water hypothesis.

  4. Water Supply And Cancer • Dr. Allen Price noticed that the percentage of patients dying from cancer in the village of Horrabridge in Devon varied depending upon the source of water. • Cancer accounted for 46% of deaths in the northern part of the village which drewing its water from Watery Ford. Cancer accounted for 8% and 15% in the middle and souther part of the village, which got its water from springs and Dartmoor respectively.

  5. Water Pollution • The water supply in large urban areas is treated and is generally fairly safe. • The water supply in smaller towns and rural areas may be more problematic. Water drawn from groundwater or lakes may be contaminated by septic tanks, slurry or inorganic fertilisers. • Water may also become contaminated in the pipes by dissolving trace quantities of lead, copper, zinc, mercury, nickel or chromium in the materials used to make the pipes.

  6. Discussion • There are a large number of potential environmental risks to health. However, it is important to keep them in perspective. • The exposure to environmental risk factors in many cases is much less than the exposure to similar factors from other sources. • Ames: 99.9 per cent of the ‘carcinogenic pesticides’ to which we are exposed come from fruit and vegetables. • PCB residues constitute 0.00000025 per cent of the oestrogenic substances in the diet.

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