It’s Raining! I Might Get Tritium in My Hair?

True or false?

True, and this blog will tell you why it happens.

We all have trouble looking at very big or small numbers and understanding their size and importance. I am one of those lucky people who have less trouble than most. This has had its downsides too.  As a child I loved mathematics and algebra. I saw the patterns in numbers easily and it was all a big game to me until I was bullied at a small country school for being different. I was tied to a post, day after day, mocked at, spat at, and even pummeled with food scraps.

Now I am a senior, maths is not so easy, but I will try and make some numbers about radiation levels easier to understand.

Tritium is a natural substance.

Tritium is formed in minute quantities every day in our atmosphere. Cosmic rays from space hit the gases in the air, mainly nitrogen, forming tritium. Tritium is a type of hydrogen atom with 2 extra neutrons in its nucleus. Tritium quickly becomes part of a water molecule.  Instead of a water molecule with 2 atoms of ordinary common hydrogen with one atom of oxygen (H2O), a few molecules of water are HTO. The chemistry of both is virtually identical.  The mixture comes down as rain.

Just how many water molecules have tritium in them? Well, this is where the big and little numbers come in, making the situation hard to visualize. A new unit was created to help scientists assess the meaning of various concentrations.  1 TU or tritium unit equals 1 tritium atom in 10¹⁸ atoms of hydrogen. 10¹⁸ is 1 followed by 18 zeros. I find that hard to visualize. Let’s try. There are 8 billion people on Earth, that is 8,000,000,000 people. That is only 8 with 9 zeros. So, we have to imagine the same number of planets as there are people on the earth, with populations similar to earth to be in the right ballpark.  So TUs are like one tritium or one person out of all those people on all those planets put together.  I still find that hard to visualize, but it does tell me that finding 1 tritium atom in all those ordinary hydrogen atoms looks impossible.  Yet scientists around the world can and do measure tritium levels in rain, river and ocean water and ground water. In Australia, ANSTO publishes some of this data.

So how high are tritium levels in rain? It is seasonal and dependent on rainfall patterns. In Australia it is 2 to 3 TU. Most numbers vary from 1 to 10 TU.  Nuclear bomb testing increased tritium levels in rain for a time but still at levels in the same sort of range, definitely measurable but extremely small.

So, what does this actually mean? What are the chances of one tritiated water molecule falling on your head? 18 g of water (3 big teaspoons) contain 6 *10²³ molecules of water. There would be a million tritium atoms in this rainwater.

Yes, if it rains on your hair, you will get natural tritium in your hair.

So the answer is TRUE.