New health and environmental risks in water for a new centry

Abstract

In those where appropriate water management and control have been implanted, hazards that have endangered Humanity throughout time have been reduced. Today, however, new threats are emerging, threats previously unknown, inexistent or considered irrelevant in the past.

The so-called chlorination by-products of water are the other face of this landmark of the employ of chlorine as a disinfectant. Its drawbacks are by no means comparable to its benefits, but in a population with higher life expectancy and health standards, epidemiological studies have determined a higher cancer risk, to a variable certainty though.

Consecuently, European Directive 98/83/CE has established a limit of 100 μg/l for the group of trihalomethanes. Compliance with this limit it’s been difficult for Spain as surface water is a main resource and, on the other hand, its warm climate favours its formation.

Extensive experiments on water fluoridation in United States and Central and Northen Europe showed, to a varying extent, a positive effect on dental caries. However, there is an increasing opinion on its side-effects with a result of both dentine and skeletal fluorosis. A number of authors state that even the current recomended dose in drinking water (1,0 to 1,5 g/l) could be deletereous. Controversy has raised throughout the last decade and has led to a tendency for suppression.

During the last quarter of the XXth century groundwater monitoring plans have revealed that arsenic is present more frecuently than it was thought. The best known episode is that of Taiwan, with a result of some 10.000 cases of melanodermic syndrome and skin cancer. Since animal studies had failed in demostrating a cancer induction or promotion with arsenic, the overwhelming records of that episode have permitted a risk estimation and, then, proposal for the new standard of 10 μg/l. A most tragic episode is that recent of Bangla-Desh, with more than 40 millions individuals affected of chronic intoxication, many of them with skin, lung and bladder cancers.

Coastal and continental water eutrophycation is a broadly generalized phenomenon, which affects Spain too. There is a recent concern about it because toxigenic algal blooms are more and more frequent. There is an estimation that half of them have produced neuro or hepatotoxins in dams and backwaters. The surface accumulation of some species of blue-green algae with crusts or foams by the shore is been known as a cause for lethal intoxication of cattle. More frequently can be found human episodes with eyes irritation, rashes, vomiting, dyarrhea, fever and muscular and articulation pain in individuals after drinking or bathing in waters with foams from algae. The new spanish regulation stablishes a control for microcystine, with a limit of 1 μg/l.

Waste waters may hold up to 100 especies of human pathogenic viruses. They usually cross through sewage treatment plants and survive in the water bodies for large periods, thus reaching the drinking water plants were they are not affected by the chlorine. However, only for a few there is evidence of transmission through water, as with the case of the Hepatitis A and E viruses. On the other hand, currently viral gastroenteritis is the second cause of infectious disease in developed countries. The agents are considered to be Rotavirus and Norovirus (Norwalk-like viruses) with a hydric transmission.

For years, Cryptosporidium has been considered an animal parasite, especially of cattle. In 1976 it was first recognized as a human pathogen, but not until 1983 it was documented the first epidemic transmitted by the water. In 1993 a big epidemic was declared at Milwaukee (Wisconsin) with some 400.000 affected, after ingestion of water from a distribution system which showed to comply with all the legal standards. In inmunosuppressed patients, the infection is severe and with a high rate of death among those affected by SIDA. Conventional chlorination does not affect the oocyst, although much of them (but not always and not all) are rettained by the filters. The risk and lack of safety is a fact, because the infective dose could be between 1 and 100 oocysts.