Xenobiotics, Option B – Biochemistry

I’ll be honest, Xenobiotics was a new one to me.  I’d heard of antibiotics – defined in my own words as ‘those chemicals that kill bacteria’, but Xenobiotics was a new one.

So what did I do? Probably the same thing as you and I googled it, getting:

‘Relating to or denoting a substance, typically a synthetic chemical, that is foreign to the body or to an ecological system’.

 So, an antibiotic then? Well, yes, and no – not just an antibiotic, it’s a bit more than just this. A xenobiotic could be a drug or ‘chemical’ present in abnormally high amounts. This latter definition could relate to a naturally occurring substance (eg, testosterone, that was present in abnormally high amounts – ie, the only way it could have got there would have been externally, it would have been introduced to the body – we are talking about athletes doping their blood here).

But when we write about a ‘chemical’ in the above paragraph, what do we mean? Well, another quick Google search takes us to http://www.issx.org/?AboutISSX which defines the chemical as being food additives or environmental pollutants.

It is easy to think that Xenobiotics are just a problem for us but it is also important to realise that they can be a problem for other members of the food chain. For example, fish that feed near human sewage can ingest human hormones that have been released in urine from women taking the contraceptive pill.

The most common environmental pollutants that are referred to as Xenobitics include dioxins and polychlorinated biphenyls.

Dioxins are produced by the unintentional combustion of organic compounds (eg, PVC) and can accumulate in our bodes. Some dioxins have been linked to cancer (source: http://www.dioxinfacts.org/questions_answers/ )

Examples include:

Image: Wikipedia

2,3,7,8-tetrachlorodibenzodioxin (TCDD)

Polychlorinated biphenyls are slightly different to dioxins and were widely used as coolant fluids until they were banned in the USA in the 1970’s (source: https://en.wikipedia.org/wiki/Polychlorinated_biphenyl ). Accumulation of them in the body was linked to endocrine problems and neurotoxicity.

A classic example of the Xenobiotic is DDT (or dichlorophenyltrichloroethane). It was used as an insecticide in the 1940’s and 1950’s and hailed a wonder substance as it would allow crops to grow without being eaten by bugs.

Image: Wikipedia

However, it was realized that it accumulated in organisms in the food chain and could lead to problems with the endocrine system and cause cancers. It’s use was banned in the USA in the early 1970’s.

This seems to be a reoccurring theme doesn’t it? We discover something new, a wonder substance, only for us to find out later it can do more damage than good.

What are your thoughts on Xenobiotics, it would be good to read and hear them. Please feel free to leave your comment below.