I was minding everyone else’s business on Twitter the other day when I cam across a tweet saying that America was now a third world country because the water was no longer safe to drink. On following the link it turned out that the problem was hexavalent chromium. Being a bit of nerd about these things my first reaction was ‘I wonder how they measure that?’ Measuring the total chromium would be easy enough, but how do you tell how much of it is the hexavalent form? (If you are thinking at this point, this guy should get out a bit more you are probably right.)
Chromium is a well known metallic element that is reasonably common and which we come into contact with quite often. It is a bit like lead and mercury in being quite toxic in high concentrations, but we are adapted to be able to handle the low levels we naturally come into contact with. We come into contact with chromium quite a lot because it comprises about 10% of stainless steel. Although the whole point of stainless steel is that it is resistant to corrosion, it doesn’t last forever. Tiny amounts of chromium will be leached into water in contact with stainless steel. So removing every atom of chromium from the water you drink is probably not practical, though I dare say you could do it if you put your mind to it. You would have to steam distil all your water in chromium free glass as the first step, so you would need deep pockets and plenty of patience.
But there isn’t really any risk from stainless steel. To get into the water it is transformed from metallic chromium into trivalent chromium. This is the most stable form. The hexavalent form is much less stable and converts to the trivalent form relatively easily. The difference is quite interesting, but I’ll refer you to chemistry text book if want more details. For the purposes of this post lets just say that the hexavalent form is rare in nature but is produced in some industrial processes. Both can be toxic at high levels, but the hexavalent form is much much more toxic.
But lets be clear what we mean by toxicity. There is a phrase that ‘the dose makes the poison’. Chromium is a very good example of this. The quantity is absolutely crucial. In fact, it is a necessary trace element in the diet so you actually need a certain amount. But is toxic at high levels.
So the news story at first sight seemed plausible. An industrial chemical had got into water courses and was causing health issues. It reminded me straight away of the Camelford incident in the UK where too much aluminium got into drinking water causing some people to get very ill. So I decided to look into the details.
The first thing I noticed was that the levels being talked about were extremely low. And when I say low, I really mean low. The highest level was 12.9 parts per billion. I did a few calculations and worked out that the amount of hexavalent chromium you would drink in a glass of water. It is so small that I don’t think that there is a balance in existence precise enough to weigh it. You would need an extremely good microscope to even see it. I tried to think of a comparison but similes failed me. Lets just say, it really is not very much. The idea that such a low concentration could be harmful, or indeed have any effect at all took some believing.
But there is something else about the chemistry of chromium. The transformation from hexavalent to the much less toxic occurs much more quickly in acidic conditions. As it happens, the stomach is highly acidic. So any hexavalent chromium you happen to drink will be turned into trivalent chromium pretty quickly. I found a recent paper that studies exactly this in detail. In this trial people were asked to ingest 5mg of hexavalent chromium. What happened to them? The hexavalent chromium was completely cleared in three days. In other words, levels of hexavalent chromium thousands of times higher than the worst data in the news story can be drunk without any ill effect whatsoever.
That doesn’t mean that it is a good idea to ignore the data in the news story. It is an industrial pollutant that could be dangerous at higher levels. It also isn’t very stable. The fact that it is found at levels of 12 ppb in one place might indicate that it can be found at a higher and possibly dangerous level closer to the source. It may be a warning of a problem. Far from being worried about the absolute levels, the variability in the data is the real message. If it ca n be 100 times higher in one place than another then maybe it is higher still elsewhere?
So are the people behind the report carrying out more work to identify the possible source of the potential problem? Well, as it happens they aren’t. Or if they are, they aren’t talking about it. The originators of the story are in fact the Environmental Working Group – and if you are a regular reader of this blog you will know that I have been less than impressed by their work in the past. It looks like they are not much better at general environmental issues than they are at creating databases of cosmetic ingredients.
The environment is a bit of an interest of mine, but I won’t claim to be an expert. It may turn out that hexavalent chromium is indeed massively more toxic than I realise. I don’t follow the literature closely enough to be confident that some work might have identified previously unsuspected risks. The trouble is that the approach taken by the EWG is just so gormless. Here is some data, they say. Isn’t it scary? What can you do? Well here is a database where you can look up to see if you are at risk. The chances are you will be. Then you have buy the filter that they recommend – preferably using their Amazon account so they can raise so money to do more ‘research’. Amusingly you can’t buy bottled water because the same group has already run a scare story on that. I suppose we have to at least praise them for being consistent.
The trouble with this approach is it is so passive. As someone who considers himself to be an environmentalist, something seems to be missing. The environment is all around us – and understanding it and how we fit into it is a great thing. There will always be problems and issues that come up. And there are always solutions. In many ways the best way to look at them is not as problems at all but as signals to change our behaviour. I love creative solutions. Even problems as big as global warming and resource depletion call up in more mind more better solutions than problems. How would sailing ships work with computers to control them and accurate GPS for example? I imagine they would look beautiful. Would we miss oil tankers?
This chromium story just cries out to be given the big picture treatment. It is an industrial pollutant. What industries? Are discharges increasing? What are the trade offs if discharges are prevented? Do the people responsible for releasing it even realise they are doing it?
I am not up to the task myself , but I would love to see a clear and simple explanation of the different oxidation states of chromium. Why is the less stable hexavalent form of chromium so much more toxic than the more stable trivalent form? How does an unstable form persist long enough to pose a risk? (The answer to that last one is probably that it doesn’t.)
You don’t get any answers from the EWG. You just get a solution offered on a plate. It’s a sort of MacDonald’s burger approach. I have a great respect for real environmentalists. The kind of person who can be a pain in the neck, but who makes you think. That is how we all learn and grow, and how things get better. Someone who just wants me to get my cheque book out makes me instantly suspicious.
I don’t sadly have the time to follow every issue that interests me so I am going to leave this one for other people to solve. But I have a feeling there is a story in here somewhere, and probably not the one spoon fed to the journalists in the press release. I doubt very much that US drinking water is now of the standard of a third world country. At the very least I think there are some valuable lessons to be learnt. If you have the time and energy I doubt you will regret time spent researching this.
And if you find out how they tell the difference between the hexavalent and trivalent forms of chromium when they test the water, please let me know how they do it.
The EWG is very good at social media and PR so it is easy to find their side of the hexavalent chromium story all over the web. This is a direct link to the study I referred to that shows just how easily the body copes with hexavalent chromium.
Toxicology and Applied Pharmacology Volume 141, Issue 1, November 1996, Pages 145-158 Absorption and Elimination of Trivalent and Hexavalent Chromium in Humans Following Ingestion of a Bolus Dose in Drinking Water B. D. Kerger, D. J. Paustenbach G. E. Corbett and B. L. Finley
After writing this post I came across this LA Times article that refers to a survey that failed to pick up any adverse effects in an area where there is abnormally high hexavalent chromium levels.