The reason for this post is that it’s a topic I’ve been working on at work and some of the things that I have found have shocked me slightly. The topic is chemical regulation, something that has never interested me before but has a big impact on our day to day lives. This is a brief commentary on its speed and what rules are used to govern it,
Firstly, a good place to start with chemicals is to understand that, for most, the dose makes the poison. So for most chemicals if you receive a low dose then you’ll suffer no ill effects. But sometimes things like timing of exposure have a big impact on humans, e.g. thalidomide, or the dose may be fine for us but not so fine for wildlife.
Secondly, there are two ways of assessing if a chemical is going to be bad for us: hazard based assessment or risk based assessment. In a nutshell, hazard based roughly says that if any chemical is bad then it should be banned, whereas risk based looks at likelihood and level of exposure as well. Risk based is probably better but only if you have good data on exposure likelihoods and levels, otherwise it’s just guesswork. This article briefly goes over the debate in Europe about which system to use: LINK. Out of this type of debate the Precautionary Principle has arisen, basically safety first, but a lot of people say that this is unscientific because it doesn’t take risk into account.
So why am I writing about this? Well as a scientist I think that risk based is probably the most sensible but after looking into two chemicals Tributylin (TBT) and Diethylstilbestrol (DES) I am not so sure anymore.
The case of TBT:
This chemical was used as an antifouling agent on boat, to stop barnacles etc growing on the hulls of ships and other aquatic craft. It did a great job, but one problem: it inhibits the Cytochrome P450, which is involved in converting androgens to oestrogen. This caused huge number of female molluscs to be unable to get rid of their testosterone and basically grown male(ish) genitalia, something called imposex. This had a huge impact on benthic organisms and impacted on algal growth and young fish too. This was discovered in the 1980s and in some countries it was banned by 1987, but even in those it still has knock on effects to this day. But it took until 2003 for the the International Maritime Organisation to finally officially phase it out.
The case of DES:
DES was used as a preventative treatment to stop women having miscarriages and its use started in 1938. However, by the 1953 it had been shown not to help with miscarriage prevention at all. Some not very nice trends started to be noticed by doctors and then Chicago’s Arthur Herbst showed that daughters of mothers who had used DES had a much higher incidence of rare vaginal cancers at early ages. It turns out that from long-term studies that women prescribed DES have higher risk of breast cancer and in addition to cervical cancer daughters are more likely to have reproductive tract problems and difficulties with pregnancy. This drug was also prescribed to girls who were too tall, to stop them growing. It took until 1971 for it to be banned in the US and 1978 for Europe.
It took a staggeringly long time for both of these chemicals to be banned for those uses, TBT worst of all because its effects were known in the 80s and it took till the early 2000s to be fully banned.
These two examples show how long it can take to show that something is unsafe and should be banned. I’m not advocating for everything that may be hazardous to be banned straight away, but the argument against using the Precautionary Principle is not as simple as Science v Non-science. We must learn from examples like these but do so by developing better and early tests for risk.