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Pretoria News recently revealed that the Rietvlei Dam, which supplies the city with water, is highly contaminated with endocrine disrupters – chemicals that are causing reproductive damage and sex changes in animals and fish (Carnie, 2007).
What’s more, research shows that foods contaminated with EDs could pose a health risk to humans (Hill, 2007).
What are EDs?
Endocrine disrupters (EDs), or endocrine-disrupting chemicals (EDCs), are chemical substances that can interfere with the functioning of the so-called endocrine system in animals and humans.
The endocrine system includes the glands (e.g. thyroid, pancreas, male and female sex glands), hormones (e.g. insulin, oestrogen, testosterone and thyroid hormone) and receptors (i.e. parts of cells that react to hormones).
The hormones produced by the endocrine glands circulate through the body and regulate countless functions. For example:
- insulin helps the body to control blood-sugar levels;
- thyroid hormone regulates metabolism, growth and development; and
- the sex hormones are responsible for normal reproduction, growth and the onset of puberty.
In other words, the endocrine system is one of the most crucial systems in the body and anything that interferes with its normal function can cause serious problems.
EDs do what their name says: they disrupt the normal functions of the endocrine system, and either cause abnormal functioning of the endocrine system or kick start certain processes, such as puberty, at the wrong time.
Effects of EDs
a) Animals
In the local study conducted at Rietvlei Dam, a team of researchers working for the Water Research Commission found that the fish and animals in the dam and its surroundings exhibited the following abnormal characteristics (Carnie, 2007):
- The ratio of male and female frogs was highly skewed – female frogs outnumbered male frogs by 4 to 1, instead of the normal ratio of 1:1.
- Snails either had no penises or much smaller penises than normal.
- Male eland developed calcified lumps in their testicles.
- About 30% of the catfish in the dam had both male and female sex organs.
- Mice had low sperm counts.
- The catfish also had high levels of DDT in their bodies (DDT is a pesticide that hasn’t been used in this area for several years).
These findings in animals indicate that the water of the Rietvlei dam is highly contaminated with EDs. And if the residents of Pretoria drink this water, they’re probably also being exposed to these toxic chemicals – a disturbing thought.
Yes, our water is put through a reasonably sophisticated purification process, which removes nasty solids and bacteria, but to remove complex chemicals would be prohibitively expensive.
Currently, no water-purification plant here or elsewhere in the world can afford to pass the water through the process (ion-exchange columns) that would remove these dangerous chemicals.
In fact, we can be pretty sure that we’re drinking water that contains EDs and that the food we eat, which is irrigated with water contaminated with EDs, also contains these chemicals.
b) Humans
Research on human subjects is not yet as extensive as on animals, but some evidence is accumulating that we’re at risk and that the effects of EDs are starting to emerge. One study cited by Carnie (2007) suggests that there are more girls than boys being born in Greenland, indicating a skewed sex ratio linked to EDs.
What we do know is that the amount of synthetic oestrogen that’s polluting our water sources because of the use of contraceptive pills and hormone-replacement therapy is escalating at an alarming rate.
Add to this the EDs arising from pesticides such as DDT and other chemicals such as dioxins and PCBs (polychlorinated biphenyls), and you have a recipe for disaster.
According to Hill (2007), the following chemicals have been linked to the following negative endocrine effects:
- Synthetic oestrogens and a chemical called bisphenol A (used in the manufacturing of food containers, plastics, can linings and water pipes) have oestrogenic effects and can contaminate foods.
- Phthalates (used for printing ink and food-packaging adhesives) cause a variety of negative effects and can concentrate in fatty foods such as butter and cheese.
- Dioxins, furans and PCBs can enter foods through the environment and are mainly found in animal products (milk, meat, fish and eggs).
- Pesticides enter the food chain via the environment and can cause thyroid, oestrogen, testosterone and androgen disruption (leading to effects such as disrupted reproduction, blocking of ovulation, growth retardation, cancer and benign tumours).
The list is endless and the implications are serious.
What can be done?
At the moment the public can't do much about this problem as so many foods appear to be contaminated.
Researchers need to expand their studies to determine exactly which chemicals act as EDs and at what level of contamination they start to affect human health and reproduction.
I believe that many 'modern' diseases or conditions, such as the metabolic syndrome, polycystic ovarian syndrome, the decline in sperm count in men, lack of ovulation in women and insulin resistance, may be linked to the silent toxins in our water and food.
Hopefully international agencies and governments, including our own, will start taking the threat of EDs seriously and come up with a solution.
Text copyright: Dr I.V. van Heerden
22 October 2007
References:
(Carnie, Tony 2007. Murky world of Rietvlei Dam. Pretoria News, 24 Sept, 2007, p 4; Hill, Sue (2007). Endocrine disrupters - Potential risks to health caused by eating contaminated foods. FoodInfo, October 2007, pp 6-7.)
