Poisons in the home

09 January 2018

Interview with

Professor Robert Chilcott, University of Hertfordshire

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Poisons may be most associated with gruesome murders, but the vast majority of poison related deaths are accidental. According to the NHS website, most poisonings in the UK occur in the home. So are there compounds lurking our cupboards that we should be aware of? Katie Haylor spoke to Professor Robert Chilcott from the University of Hertfordshire...

Robert - If we stick to the consumer products, one of the more interesting ones in botulinum toxin. Sometimes, if food has not been processed properly, things which are stored and boiled in jars in tins can actually grow certain types of bacteria which produce botulinum toxin - botox.

Katie - That’s right, you heard correctly: botox is the same stuff that some people have injected into their faces to relax facial muscles in order to reduce the appearance of lines and wrinkles - it’s the same toxin.

Robert - It only counts for a very small fraction of percent of all reported food cases, but it’s really the one you don’t wish to have. It nearly always requires hospitalisation and about one in ten people who get botulinum toxin will actually die.

The medical form, of course, is very pure and it’s a specific form of botulinum toxin. In the wild there’s about seven types of botulinum toxin but they all have the desired effect; they’re incredibly toxic. I think botulinum toxin is the most toxic substance that we’re aware of.

Katie - So bacteria produce this toxin, and this bacteria could be around in the food that goes into the can, so what happens then? How, if you’re unlucky enough to eat this food, what happens to your body?

Robert - The bacteria that produce the toxin are pretty much ubiquitous. It grows nearly everywhere, so almost certainly, it will be in the food that you try and preserve. The problem comes when you don’t follow the right instructions. For example, if it’s not boiled properly or you keep it in a solution which is not sufficiently acidic, then you run the risk of the bacteria starting to produce the toxin, which is primarily under what’s called anaerobic conditions, so anything that doesn't’ have too much oxygen in will be a nice breeding ground for botulinum.

As I said, it’s an incredibly toxic material. The estimated lethal dose is about 70 nanograms. A nanogram is about a thousand millionth of a gram, so it’s very difficult to put that weight, or lack of weight, into perspective. But, as a rough guide, if you think about a single hair, that would be about 9,000 times heavier than a lethal dose of botulinum toxin.

Katie - Is this something that we should worry about as consumers of tinned foods, or does the problem come when you’re making your own tinned food?

Robert - I think the mass market, the processing now is to a point where we don’t need to worry about this at all. Of course, if we’d lived about 100 years ago when tinned food was just coming into fashion, that probably was more a game of Russian roulette. The most common forms of botulinum toxin these days is people who preserve the food at home: pickles and so forth and things which goes into jars. Fruit, in particular, because sometimes it lacks the acidity that you need to prevent the botulinum from growing. But, in general, it’s actually, as I’ve said, a very rare form of food poisoning.

Katie - Why is it so poisonous? What does this toxin do when it gets into the body?

Robert - To put it simply, the botulinum toxin works by turning off our nerves. As you probably know, nerves normally activate muscles using substances called neurotransmitters. These are chemicals that are released from the nerve endings and result in the coordinated movement of muscles, so when we speak or walk or breath, this is all down to the nervous control of our muscles.

Basically, the toxin acts by cutting off the ability of the nerve endings to produce the neurotransmitter. Essentially, that stops the muscle from being told to contract and, eventually, it just causes paralysis. What’s particularly nasty about botulinum toxin is that you get these paralysis effects and, eventually, you are unable to breath, but the whole time you're actually conscious and aware of what’s going on.

There is an antidote; it’s based on antibodies that actually bind to the different types of the toxins. There are seven different toxins in botulinum toxin. If you manage to get to a hospital and diagnosed then that antidote may be available. Otherwise, the only treatment really is supportive - you may need to have mechanical ventilation. But botulinum poisoning can last quite a long time so you may still suffer different degrees of paralysis for many months after you’ve initially been poisoned.

Katie - Wow. So if you’re thinking about making your own tinned foods you do need to be exceptionally careful. What about non-consumer products then; what about, for example, cleaning products can they be poisonous?

Robert - Oh, there’s a whole wealth of poisons in cleaning products. The obvious example may be chlorine. Most people have heard of chlorine, but it’s a bit of two-edged sword when it comes to our society. On the one hand you have your chlorine-containing consumer products that keep our world nice and clean and fresh and free from major diseases. But, of course, if you mix the wrong type of cleaning products together you can quickly produce lethal quantities of chlorine. It’s not uncommon: I think in the UK each year there’s about half a dozen major incidents involving public exposure to chlorine. There are probably a small number of incidents involving single people, people have mixed these chemicals in their toilet.

But chlorine is actually quite toxic. It’s a very highly reactive molecule and it likes to seek our moist areas, so when you breath it in the nice wet lining of your lung tends to absorb the chlorine. There’s no specific mechanism of action, it’s just nasty corrosive stuff. In a sufficient dose, you get the chlorine inside and it’ll basically just rot the lining of your lungs. That then causes a condition called pulmonary edema so, basically, all the fluid that’s inside our body starts to leak into the lungs and it stops us from breathing.

Katie - What kind of toxic combination are we talking about?

Robert - The rough rule of them is: don’t mix cleaning products. But the particular cocktail which has the worst effect is mixing a bleach solution with anything which is acidic or contains ammonia.

Katie - Household bleach contains sodium hypochlorite, a chlorine compound. It’s a common cleaning product often used as a disinfectant to clean toilets, swimming pools, and even to treat public water supplies. But, when mixed with other cleaning products, toxic gases can be released. For instance, chlorine gas in the case of mixing with acidic substances, or chloramine gas in the case of mixing with alkaline products like ammonia.

Robert - The initial signs of poisoning are relatively low concentrations, it’ll cause mild irritation of the eyes and the lungs. So, basically, it’ll be like going to a swimming pool for maybe an hour or so. You get a bit of red eye, maybe a little tickly cough. But when you start to get exposed to a higher concentrations it can get quite painful to breathe and breathing becomes much more difficult. When you go to a very high level - we’re talking about 300 parts per million or so - you can actually die within 30 minutes of exposure.

People often talk about antidotes to poisons but, I think, there’s only maybe about a dozen antidotes in the whole world for very specific chemicals. Unfortunately, chlorine is not one of them. So, basically, if someone gets exposed to chlorine and has these severe effects the only way to treat them is supportive. You give them some oxygen, you may want to give them some drugs to open up the airways, which are known as bronchodilators, possibly steroid to try and reduce the inflammation. And, if they’re lucky, it can take maybe three, four, five weeks to recover from a significant exposure to chlorine.

Music: Daniel Birch & Ben Pegley

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