HEALTH & GEOLOGY

1. HEALTH & GEOLOGY There can be a relationship between the geology of an area and certain diseases of people, plants & animals, due to abundance or shortage of certain elements, or presence of certain minerals or radon gas. Anthropogenic activities may increase the natural level of toxic elements by mining, manufacturing, usage or disposal of waste.

2. Medical geology multidisciplinary field of science to study the effect of geological interactions between rocks, soil, water and air on the health of people. It includes: (1) Natural hazards such as the effect of volcanic gases, toxic elements in ground water, land slides etc. (2) Enhanced hazards due to anthropogenic activity such as acid mine drainage and the release of Hg due to gold mining in Brazil.

3. Toxicology: study of toxins Effect of substance on population as a whole, but individual reactions may vary Elements may work together to enhance or reduce the effectiveness or toxicity of an element. Epidemiology: study of epidemic Study of the statistical occurrence of diseases and factors such as trace elements in diet or smoking. May find areas with high or low concentrations of an element have high or low occurrence of certain disease. Epidemiological hypotheses must be proved with controlled laboratory experiments to discover the actual effect of the element either alone or in conjunction with other factors.

4. Detrimental to Health TRACE ELEMENTS

5. TRACE ELEMENTS Essential for the production of living tissue: H, Na, Mg, K, Ca, C, N, O, P, S, Cl Necessary in trace amounts: F, Cr, Cu, Zn, Se, Mo, I, Mn, Co Cause health problems in high concentrations: As, Ba, B, Cd, Cu, Cr, F, Pb, Hg, nitrates, Se, Ag, Na All trace elements are available in rocks but amount may depend on: the type of rock and geological environment the dominant weathering processes the soil cover. Trace element problems improve as we eat food from many different areas but drinking water is usually local

6. CONCENTRATIONS in NATURE

7. DOSE RESPONSE CURVE Many elements essential for health in small doses, become toxic and even lethal in higher concentrations. Threshold A: Less than this value is harmful A-B: increasing benefit B-C: maximum benefit C-D: declining benefit D: threshold of increasing harm, toxic E: noticeable harm F: death Values of ABCDEF not necessarily known for each element or form of life For each element the thresholds are different

8. FLUORINE Dental Caries F- is smaller with the same charge as OH- Has a higher charge to mass ratio so repels anions efficiently. F- can replace OH- in minerals Bones & teeth made of apatite Ca5(PO4)3(F,Cl,OH) Fluoro-apatite grows larger and stronger crystals than hydroxy-apatite. F can make bones and teeth stronger and more dense Helps with osteoporosis and tooth decay Osteoporosis % of decreased bone density in areas of high or low F in drinking water

9. Greater than 8 ppm can cause excessive bone formation and calcification of ligaments, Often seen in cattle eating F-rich grass and in people drinking from confined aquifers high in fluoride B, Mo, Li reinforce the effect of F; Se reduces the effect School girl in Sri Lanka in a region with high F in ground water

10. Geological Occurrenceof Fluorine (ppm) Igneous rocks and clays Less common in sandstones and limestone F added to drinking water in areas of low abundance.

11. IODINE and SELENIUM Similar biogeochemical cycling including concentration in ocean water and atmospheric transport Released from oceans by (1) seasalt aerosols (e.g NaI) (2) biogenic gases (e.g. CH3I) Marine plants and animals have higher Se and I than ocean water which causes the surface to have higher concentrations due to the abundance of biota. I & Se concentrated in the upper layers of soil by atmospheric precipitation from ocean spray or by biological action in soils, then be remobilized into surface water.

12. Iodine Cycle

13. IODINE is an essential trace element Lack of iodine causes Iodine Deficiency Disorders (IDD): (1) goitre (enlargement of the thyroid gland). (2) stunted growth and mental development in children whose mothers have iodine deficiency. WHO estimates >1 billion people at risk from IDD Woman with a goitre from Sri lanka

14. Relationship between low iodine and IDD Low iodine concentrations are linked with a high incidence of goitre in areas where glaciation removed the topsoil e.g. goitre belt in northern US states & S. Canada. Iodised table salt or iodized cooking oil supplements drinking water Winnipeg

15. 131I released after nuclear explosion (e.g. Chernobyl) moves rapidly into food chain and may lead to thyroid cancer. People given iodine tablets to saturate thyroid with non radiogenic iodine.

16. SELENIUM O.04 ppm Se essential Se deficiency causes muscular degeneration, impeded growth, fertility problems, anaemia, liver disease 0.04-0.1 ppm Se beneficial 4 ppm toxic: Cattle eating plants rich in selenium (loco-weeds) get the "blind staggers" muscular dystrophy and appear drugged. e.g. in San Joaquin Valley, California Dose Response Curve for Se 0.04 0.1 4.0 (ppm)

17. Geological environment of selenium (ppm) Primary source: volcanic activity Concentrated in: hydrothermal sulphide veins U deposits. in soils by plants and animals Concentration ranges from 0.1 to 1200ppm. Solubility depends on pH and Eh Se has 4 oxidation states: -2 H2Se: toxic and reactive gas 0 Elemental Se: insoluble & unreactive +4 SeO32- selenite: toxic but easily reduced to elemental Se0 +6 SeO42- selenate: very soluble and toxic

18. MERCURY, CADMIUM, LEAD toxic enzyme inhibitors. Can be methylated by bacteria, cross the blood/brain boundary High Cd, Pb & Hg in the brain cause impairment of neurological functions and congenital defects. Bioaccumulate: become concentrated in plants, animals, fish

19. Geological Occurrence Cd, Pb Concentrated in economic hydrothermal sulphide mineral deposits and released during mining and mineral processing, and industrial use

20. Geological Formation of Hg Hydrothermal ore formation Note the natural emissions of Hg to the atmosphere from volcanoes and fumaroles

21. Toxicity of mercury Knowledge of toxicity from miners. Roman slaves and Spanish convicts had an average life expectancy in the Hg mines of 3 years Causes loss of teeth, tremors, loss of strength, psychological problems. Mad Hatter disease due to use of mercuric nitrate in felting of fur for hats Methyl mercury extremely toxic

22. Minamata, Japan 1956: People in a fishing village of Minamata developed blurred vision & speech, numbness of limbs (Minamata Disease) This was caused by the release of methyl mercury in industrial waste water from the Chisso Chemical factory upstream 1959: the pollution problem and source were identified but the dumping continued until 1971. By 2001, 2,265 victims had been officially recognized (1,784 of whom had died) and over 10,000 had received financial compensation from Chisso.

23. Mining Cinnabar mined at Amaden Spain since 430 BCE. HgS heated to release elemental Hg as a gas which is condensed

24. Historical uses of mercury Since 4000 BCE Cinnabar used for the preservation of human bones including Egyptians Since Egyptian/Roman times cinnabar used as paint pigment, cosmetic, pottery glaze, anti fouling on ships, red ink. Romans: Extraction of elemental Hg by distillation and amalgamation with gold Middle ages: Hg amalgamation used in alchemy and early chemistry leading to the discovery of 22 elements Medicinal use since 460 BCE (Hippocrates) and since 16th century as a cure for syphilis, and as a diuretic, antiseptic, contraceptive Still used in dental amalgam, preservative in flu vaccines (Thimerosal), herbal remedies