Tap water under microscope
24 September 2007, 06:22
Evidence of chemically induced sex changes, sperm damage, missing penises and other sexual problems in fish and animals has raised fears about a potentially wider threat to South Africa's human communities.
The pioneering study by a team of senior Water Research Commission scientists found evidence of reproductive damage, as well as high cancer risks in a wide variety of animals at Rietvlei, a large nature reserve on the outskirts of Pretoria and Johannesburg.
While the commission has described the study as a "cause for concern, but not panic", it has also raised the possibility that people around the country may be exposed to smaller but similar chemical health risks from tap water - despite sophisticated municipal water treatment systems that are designed to filter out the most harmful chemical levels.
Many of the problems at Rietvlei have been linked to a variety of widely distributed gender-bending substances known as endocrine disrupting chemicals (EDCs).
A growing body of international research suggests that even small traces of these synthetic or natural chemical cocktails can disrupt the body's chemical messaging system by mimicking the female sex hormone (estrogen), or by counteracting the male sex hormone (androgen).
The side-effects in humans are still under investigation, but some researchers have linked them to declining sperm counts in men in Western nations, delayed or premature sexual development in girls, and birth defects in young boys such as cryptorchidism (undescended testes) or hypospadia (a defect in the normal opening of the penis).
South Africa's water quality guidelines do not define or regulate EDCs, and very few tests have been done on local tap water supplies to assess the potential threats.
The studies at Rietvlei have revealed:
A highly skewed sex ratio in frogs. Females outnumbered males by four to one, whereas the normal ratio is one to one;
Some snails had no penises or smaller-than-average penises;
Male eland antelope had strange, calcified lumps in their testicles;
Nearly 30 percent of male catfish were classified as "intersex" because they had both male and female sexual organs, including the ability to produce early-stage female egg cells;
Mice had low sperm counts and other problems; and
A surprise finding was the discovery of "very high" levels of the pesticide DDT in catfish - even though the pesticide had been banned for several years in South Africa and was only used on a restricted basis for malaria control in three provinces.
DDT and its byproducts have been linked to low sperm counts and other reproductive damage to men in recent studies in Mexico and Limpopo province.
Many other potentially gender-bending chemicals are also in daily use in the homes and gardens of humans in products such as plastic food wraps, medicines, cosmetics, flexible PVC pipes, pesticides and building materials.
The first evidence of some EDC chemicals in South African drinking water was detected in a pilot study five years ago, prompting scientists to develop early warning signals in so-called "biological sentinel" animals which live in water-dependent environments.
The new Water Research Commission report on animal changes at Rietvlei coincide with international studies which suggest that more girls are being born in Greenland - one of the first pieces of evidence of a skewed sex ratio in human communities linked to EDCs.
The lead scientists of the South African study have declined requests from The Mercury to elaborate on the significance for humans, and the Department of Health has not responded to queries that were sent to it last week.
However, project team leader Professor Riana Bornman, from the University of Pretoria's department of urology, has recommended several areas of follow-up research - including chemical tests on tap water in the Tshwane Metropolitan area and an investigation into the number of people exposed to polluted water in the reserve and immediate vicinity.
Neil Macleod, the head of water and sanitation in the eThekwini Municipality, said: "This is an issue we have been looking at for about four years, but it's not something we are concerned about right now.
"Internationally, the EDC issue is at such an early stage of understanding that there are some authorities who say it poses a serious threat to humans, while others say it's hard to prove anything yet.
"We don't want to overreact or underreact," Macleod said.
The pioneering study by a team of senior Water Research Commission scientists found evidence of reproductive damage, as well as high cancer risks in a wide variety of animals at Rietvlei, a large nature reserve on the outskirts of Pretoria and Johannesburg.
While the commission has described the study as a "cause for concern, but not panic", it has also raised the possibility that people around the country may be exposed to smaller but similar chemical health risks from tap water - despite sophisticated municipal water treatment systems that are designed to filter out the most harmful chemical levels.
Many of the problems at Rietvlei have been linked to a variety of widely distributed gender-bending substances known as endocrine disrupting chemicals (EDCs).
A growing body of international research suggests that even small traces of these synthetic or natural chemical cocktails can disrupt the body's chemical messaging system by mimicking the female sex hormone (estrogen), or by counteracting the male sex hormone (androgen).
The side-effects in humans are still under investigation, but some researchers have linked them to declining sperm counts in men in Western nations, delayed or premature sexual development in girls, and birth defects in young boys such as cryptorchidism (undescended testes) or hypospadia (a defect in the normal opening of the penis).
South Africa's water quality guidelines do not define or regulate EDCs, and very few tests have been done on local tap water supplies to assess the potential threats.
The studies at Rietvlei have revealed:
DDT and its byproducts have been linked to low sperm counts and other reproductive damage to men in recent studies in Mexico and Limpopo province.
Many other potentially gender-bending chemicals are also in daily use in the homes and gardens of humans in products such as plastic food wraps, medicines, cosmetics, flexible PVC pipes, pesticides and building materials.
The first evidence of some EDC chemicals in South African drinking water was detected in a pilot study five years ago, prompting scientists to develop early warning signals in so-called "biological sentinel" animals which live in water-dependent environments.
The new Water Research Commission report on animal changes at Rietvlei coincide with international studies which suggest that more girls are being born in Greenland - one of the first pieces of evidence of a skewed sex ratio in human communities linked to EDCs.
The lead scientists of the South African study have declined requests from The Mercury to elaborate on the significance for humans, and the Department of Health has not responded to queries that were sent to it last week.
However, project team leader Professor Riana Bornman, from the University of Pretoria's department of urology, has recommended several areas of follow-up research - including chemical tests on tap water in the Tshwane Metropolitan area and an investigation into the number of people exposed to polluted water in the reserve and immediate vicinity.
Neil Macleod, the head of water and sanitation in the eThekwini Municipality, said: "This is an issue we have been looking at for about four years, but it's not something we are concerned about right now.
"Internationally, the EDC issue is at such an early stage of understanding that there are some authorities who say it poses a serious threat to humans, while others say it's hard to prove anything yet.
"We don't want to overreact or underreact," Macleod said.
- This article was originally published on page 1 of The Mercury on September 24, 2007
Pretoria
