Geogenic Contamination
Geogenic contamination refers to naturally occurring elevated concentrations of certain elements in groundwater (such as arsenic, fluoride, uranium or selenium) which have a negative health effect on humans consuming this water. Geogenic contamination of groundwater might be a result of geochemical characteristics of the aquifer material - eg. high concentrations of the contaminant in the rock matrix, dissolving during water-rock interaction, or occur due to environmental conditions such as an arid climate or reducing conditions in the aquifer which facilitate the contaminant to occur in a more mobile state.
The most wide-spread geogenic contaminants are arsenic and fluoride, affecting the health of hundreds of millions of people worldwide.
Fluoride
Fluoride is the 13th most abundant element in the earth’s crust (625 mg/kg) and exists in trace amounts in almost all groundwaters across the world. According to estimations from UNESCO, more than 200 million people worldwide rely on drinking water with fluoride concentrations exceeding the present WHO guideline of 1.5 mg/L. Fluorosis, associated with elevated fluoride concentrations in drinking water has been reported in a range of countries.
While low fluoride intake may prevent dental caries, excess
intake causes different types of fluorosis; primarily dental and skeletal fluorosis. White line striations on the teeth
followed by brown patches and, in severe cases, brittling of the enamel are
common symptoms of dental fluorosis. This is not only a health problem but also
has psychological and social impacts, as people are ashamed and possibly
ostracised due to their bad teeth. Skeletal fluorosis first causes pain in
different joints, then limits joint movement, leading to stiffness and skeletal
crippling. Besides dental and skeletal fluorosis, other manifestations such as
nervousness, depression and muscle weakness have been reported in connection
with high fluoride intake.
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| Dental fluorosis | ||
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| Skeletal fluorosis |
Arsenic
The WHO guideline value for arsenic in drinking water has been set to 10 µg/L, though in several countries higher values are used (e.g. 50 µg/L in China).
High arsenic concentrations in groundwater have been found
to be responsible for health problems summarized under the term arsenicosis,
which develop over a period of several years. Symptoms of arsenicosis range
from skin disorders (melanosis, keratosis) to cardiovascular diseases, cancer
and the impairment of the neurodevelopment of children. Since there is no cure
for arsenicosis to date, the provision of safe water for the prevention of this
disease is the vital mitigation approach.
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| Keratosis as an indication of arsenic poisoning | ||