Are home products flammable?

From time to time I get asked whether any home products that we buy are a fire risk, particularly products with a flammable diamond like one of these:

What do these mean?

The flammable liquid label will be on many solvents such as metho, acetone, xylene or turps. The flammable gas logo will be on many aerosols, as they mostly use hydrocarbons such as butane or propane.

Flammability is determined by a test where they heat the liquid and expose the vapour above it to a flame. If the vapour flashes (ignites) below 61°C it is termed as flammable, and if it flashes above 61°C it is non-flammable. This means that it doesn’t need a diamond, and there are no special transport procedures involved.

If it burns at a temperature above 61°C it is termed “combustible” – like diesel. That’s why when you see a truck go past with “Combustible Liquid” written on the panel at the rear of the truck.

Now if these liquids are flammable then, yes, if you light them they will burn. So if you spill 20 litres of paint thinners on the floor, and then while you are thinking about how to wipe it up you light a smoke and toss the still-burning match onto the xylene you will have a problem. But that is about the only circumstance where you will have a problem.

But as far as the flammable gases go, there are unfortunately cases where explosions have occurred when people didn’t read the instructions. These have all been caused by foggers, such as this

Image result for mortein control bomb

What happens is this – people in a house or restaurant realise that  they have a  cockroach problem.  So they look on the back  of the can and realise that they will only need three or four cans for the entire  establishment .  But then they think ” if three cans will work then 30 cans will work better.”  And here’s where the problem occurs.

You see for a flammable  gas there is something called a lower  explosive limit (LEL),  which refers to the concentration of gas required to initiate an explosion.  Used according to the instructions you would never reach the LEL,  and there would be no problem. But  if you ignore the  warnings on the back of the can and use 10 times the number of tins required,  then you can reach the LEL,  and this is exactly what happened in a restaurant in Melbourne a few years ago.

But ordinary aerosols  use a  flammable gas in conjunction with a water based emulsion. This means that they won’t burn. But I can remember  many years ago, , before the advent of water based formulas, a can of Mortein made an excellent flamethrower. You simply spray the contents of the can over a burning match and voila. But these products are long gone.


Is Water Fluoridation Safe?

The short answer is yes, it is, but it’s easy to understand why some people think it isn’t.

When we look at chemical toxicity, we need to understand that there are several different classes.

Firstly, there are chemicals for which any level of exposure is undesirable, as with sufficient exposure over time they will have an effect on our health, possibly with lethal outcomes. In this category we have asbestos, lead, and any of the tars and other combustion products in cigarettes.

There are other chemicals, however, which although toxic in higher concentrations, are either completely harmless, or even beneficial at low levels. In this category we have most transition metals such as copper, zinc and iron.

And fluoride.

But the trouble is that this is not obvious if you look at the data, and fluoride is a case in point. If you look at the MSDS for sodium fluoride you find that it is an S7 poison – the highest category. Little wonder that some people are leery about having it in their water.

So what does fluoride do in your body?

Mostly, it reacts with your bones. In this regard it is unusual, as most other toxins attack your organs somehow. But the fluoride attacks your bones. This is why in Breaking Bad it is the chemical of choice for disposing of bodies…..

So if you are exposed to enough of it to be harmful it causes horrible internal burns which are very difficult to treat. Whenever I have had to handle hydrofluoric acid (it’s used to make industrial strength brick cleaner) I’ve gone the full monty in terms of protective gear.

But in water it’s nowhere near this strength. The fluoridating agent in municipal waters is fluorosilicic acid, a by-product of aluminium production, and it gives a level of fluoridation of about 2mg/L.

At this concentration it is too low to be harmful – no matter how much water you drink – but it still reacts with your teeth. I don’t think anyone quite understands the mechanism, but it would be some sort of inorganic composite where the fluoride combines with the calcium phosphate (that your teeth are made of) to produce some sort of calcium fluorophosphate, that is in some way chemically resistant to the chemical decay process (caused by lactic acid that is made by anaerobic bacteria).

And this has certainly been confirmed by every study in this area – so you may drink municipal water – and use toothpaste, with absolute confidence that your teeth are being protected.

Is Julian Cribb Right?

Last week, during Dr Karl’s segment on 720 ABC radio in Perth, he had a guest by the name of Julian Cribb, who has recently written a book entitled “poison planet”. This book follows up other books with such cheery titles as “The Coming Famine” and “White Death.”

I had never heard of him before last Thursday, but he apparently passes himself off as a “science writer.” When I looked into it, all I could come up with is that he is a journalist, with no mention of any scientific qualifications.

I sent him an email to find out what his qualifications were, but have not as yet received a reply.

Anyhow, over the space of a few minutes on 720 last Thursday he managed to imply that anyone who breastfed babies was giving them “a mouthful of pesticides” and that we shouldn’t use plastic baby bottles as they contain toxic chemicals.

By the end of the show panicked mothers were texting in to ask whether they could use stainless steel bottles to feed their babies, and one mother said “thanks for making me feel like I’m poisoning my baby.”

Let’s look at these two claims and see what the science says.

The use of pesticides in Australia is controlled by the APVMA (Australian Pesticides and Veterinary Medicine Association). Essentially, it is impossible to use a pesticide in Australia without a licence from the APVMA.

This applies to the cans of fly sprays that you buy from the supermarket, commercial pest controllers, and also fruit growers.

Most people don’t know this – they think that fruit growers have open slather to spray whatever the hell they want onto their crops as often as they want, just so long as the fruit gets to market intact. But the very opposite is the case.

They must apply to the APVMA for a licence for any pesticide they wish to use. And this licence does not just refer to the particular chemical, but to every aspect of the procedure. That is, they must specify the exact concentration of chemical used, the coverage rate (litres sprayed per acre), spraying frequency, and withholding period. The withholding period refers to the time period between the last spray and the arrival of the fruit on the supermarket shelves.

Growers must keep a log of their spraying schedule, as it is subject to inspection at any time. And on top of all this, inspectors go to the markets where they take fruit directly off the trucks, and take them to a lab for testing. Any occasions where the level of pesticides on fruit is above the guidelines results in hefty fines.

So can the APVMA be trusted?

Well, it depends who you talk to. Fruit growers see them as the Gestapo, because their extremely conservative approach places a great burden, both practically and in terms of the regulatory requirements on them.

And they are certainly conservative. The amount of pesticide that they allow to be sprayed, or to remain on fruits, has safety factors upon safety factors upon safety factors. For for example, one of the measurements they use is the NOEL (No Observable Effect Limit).

This is a clinical number which tells you what level of a chemical you can have in your bloodstream before any effect whatsoever is observed, no matter how minor. To give you an idea of how conservative the APVMA is, they take this number and divide it by 10. This is a bit like saying that the best way to make sure you don’t get a speeding ticket in a 60 km/h zone is to go no faster than 6 km/h.

And there are other safety factors as well. But from the consumer’s point of view, you can have absolute confidence that none of the fruit that you get off the shelves has anywhere near enough insecticide to remotely approach a level where it could have any possible tiny effect on your health. As a matter of fact when they take the fruit for testing, most results come back as being below the level of detection of the extremely sophisticated insensitive analytical instruments that are used.

And part of this is the actual chemicals that are used. Years ago, chemicals like DDT were popular for the simple reason that they were stable – that is, they didn’t degrade in the environment. The shoe he is now completely on the other foot, and all pesticides used these days are biodegradable – that is, they degrade quickly when exposed to air or sunlight.

So the bottom line is this – Julian Cribb is completely wrong. Under the present regulations, there is just no possible way that any person could ingest pesticides off fruit that they eat to harm either themselves or their children.

The other claim he made was about plastics, and that they are unsafe for children. The implication, I suppose, is that being petrochemical products, these products are inherently evil, as we all know that oil companies are evil.

Again, this does not stack up. The only chemical that has been raised as a concern in plastic bottles or plates is bisphenol A (BPA). In sufficiently high levels, this chemical can act as an artificial hormone, which is similar to the mechanism of DDT.

Many studies buy both American and European food safety authorities, however, have determined that in the levels that BPA finds its way into food, there is simply no argument to suggest that it is a health hazard.

This, however, does not stop people who market baby products selling plastics that are “BPA free”, so if you want to be really, really, really sure, you simply buy these.

The other thing you can do is to look on the bottom of the item, where there will be a little triangle with a number in it. This is a recycling code that recyclers use to sort products into the right categories. The only classes of plastics that could even possibly contain BPA are those in categories 3 (PVC) and 7 (polycarbonate), so if you just avoid these, then you have eliminated even the possibility of your children consuming any BPA.

So if you threw out all your plastic bottles after listening to the show last Thursday, rush out to the SULO and retrieve them. Actually, don’t – buy new ones.

One warning about plastics, however – make sure they are microwave safe before you blast them. If in doubt, put the empty vessel into the microwave and zap it. If it gets hot, it’s not microwave safe.

Why is Fertilizer Explosive?

Why is fertilizer explosive?

The answer is not obvious, and for years after the invention of ammonium nitrate, people didn’t actually know it was explosive. It was only after the Texas City Disaster that the penny dropped.

Ammonium nitrate is of course a completely synthetic product, which was only created after Fritz Haber in 1913 worked out how to convert nitrogen from air into ammonia. This process opened the way for the manufacture of nitrogen containing compounds as fertilizers.

So why is it explosive? Well it’s not too hard to understand if we look at the anatomy of an explosion. An explosion is simply a rapid combustion (oxidation) process. Coal burns, wearers coal dust explodes. The only difference is the rate.

When something burns, two components are required – the fuel and the oxidant. Usually, the oxidant is simply the oxygen in air. If we were to consider, for example, the combustion of the simplest hydrocarbon, methane, the reaction would be:

CH4 + 2O2 = CO2 + 2H2O

In other words, the flammable methane requires air to burn. This is why your car needs air to run. Without air, the fuel cannot burn. This is also the reason why people put turbochargers on engines – the extra air gives you extra oxygen and therefore a more rapid combustion rate.

Well, this is the chemical structure of ammonium nitrate

you will notice something interesting about it – it contains three oxygens already. What this means is that for it to burn, (or explode) it doesn’t need any air, as it supplies its own oxygen. This means that once the combustion process begins, there is nothing to stop the rate escalating rapidly, and hence the explosion.

Incidentally, this is the same principle behind rocket fuels, but that’s another story.

Toxic Gas at Burswood?

Reported on the news tonight was a “toxic chlorine gas” scare at the Burswood resort. It apparently was caused by construction workers “mixing chemicals” and making a toxic gas cloud.

What might it have been?

Well, if we know it was “chlorine” there are two options. Firstly, any acid mixed with bleach will produce chlorine gas. Secondly, ammonia mixed with bleach will produce chloramines.

The two have a similar smell, with chloramines being the smell we associate with pools – the smell at a freshwater pool is actually due to the chloramines made by the reaction of chlorine bleach (hypochlorite) with amines (urine, skin residue etc) in pools.

How toxic are they?

Well, they belong to a class of chemical where their bark is worse than their bite. In other words, the intense smell scares you away before the concentration ever gets high enough to affect your health.

But the people at Burswood didn’t know this, and may have associated the intense smell with an affect on their health, and thus psychosomatic symptoms appear. This is almost certainly the case with the five people that were hospitalised for observation.

It reminds me of an incident at Tullamarine airport a couple of years ago when reports spread of a toxic gas leak in the terminal. Panic spread and several people collapsed and were taken to hospital. When the emergency services arrived however, they found absolutely nothing.

So there you have it – if you blast your shower with bleach to kill the mould, and come out spluttering and coughing, don’t be alarmed – it’s not hurting you.