Toxicity - where do I begin?

It's easy to think that toxicity is a much simpler subject than it really is. 

From an early age, you are likely to have been told that certain things, like for example, bleach, are poisonous. There are cleaning and medical products that are sold in containers that are "childproof" to avoid children opening them and being damaged or killed by their contents. We even have closures on doors specifically designed to be hard for children to open so that they can't get to any cupboards containing these products. Putting to one side for one moment whether any household actually needs this products (I would argue they do not) does that cover off poisons? Is everything else OK? Simply put "no, but it's complicated".

When I was at university, I had a 6 month work placement at a manufacturer of spectrometers (devices that allow you to determine the components of a material). My boss was a man called Jerry. I didn't really understand him and, despite spending a lot of time with him, I was confident that we saw things fairly differently. He struck me as a man who was comfortable with the way science worked and was progressing and I definitely was not. That was until one day he was giving me a lift somewhere. This was in the 1990's and, at the time Genetically Modified Organisms were beginning to gain popularity. From my perspective this was entirely unnecessary tinkering with nature and likely to end badly. What surprised me was Jerry saw it the same way. I still remember what he said about GMO's being a crazy idea and that "in 50 years time, we'll find out that they give you kidney lesions" and then what would we do? Research done in 2014 indicates that Jerry was probably onto something, however, where do we go from here?

In chemistry, there is a term call the "LD50". This is the dose at which 50% of animals given the substance die. The results are expressed as the amount of the substance per unit of body weight, such as milligrams per kilogram. You can find out more about this term here, but, again, is this enough to know how a substance impacts your body? What about lower levels of toxins? And how do you establish how much someone absorbs? Standards typically talk about how safe concentrations for a substance when it is rinsed off rather than left on the skin, but is that really enough information? This is where, in my opinion, it all gets extremely complicated. 

No one could say eating one chocolate bar is going to give you tooth decay. There are many people who eat lots of sugary chocolate bars and have cavity-free teeth. Does that mean that chocolate bars have no impact on your teeth? From what I have read, my personal experience and stories I have heard from others, I would conclude "no". However, how could research be designed to show that? And, even it if did show that there was a particular consumption rate of sugar that would lead to cavities, there can also be mitigating factors. For example, some people are likely to eat other foods that build their teeth up more, That would offset the impact of the chocolate bars. There will also be significant variability between people - different people will have relatively strong and weak body systems and parts - how do you account for this? Lack of sleep might have a bigger impact on the instability of their blood sugar level than certain foods. Then there are psychological factors, such as living in an abusive relationship. How can you factor that in to the impact on their metabolism and teeth? And teeth are a fairly simple example. 

What if we start talking about gut health? Studies looking at the bacterial composition of human gut has revealed more than 3000 species. That's a lot of different types of bacteria behaving in a multitude of ways impacting human guts and health. What if a synthetic chemical absorbed into your system damaged just one of these species? Research shows that not all chemical pollutants are going to impact all bacteria in the same way, so this is a probable scenario. It's likely that not all subjects on whom the product was tested would have that bacteria in their gut. Many people would have different bacteria doing a similar job, so the chemical would not affect them. Also, it might take several doses over many years for an issue to occur for some people and a matter of days for others. And, once that bacteria in your gut has been killed, how do you get it back? Some people might be consuming a diet that means they quickly recolonise their gut. Others might not. Again, this is just one tiny part of the picture.

It's pretty easy to identify a substance that kills people with small doses. It's very hard to identify a substance that slowly degrades part of a person's body to the extent that they ultimately experience ill health. And, when it comes to product development, it's too multifactorial, would take too much time and would make use of many components impossible.  I think Einstein put the challenges of scientific research well when he said: 

The scientific theorist is not to be envied. For Nature, or more precisely experiment, is an inexorable and not very friendly judge of his work. It never says “Yes” to a theory. In the most favorable cases it says “Maybe,” and in the great majority of cases simply “No.” If an experiment agrees with a theory it means for the latter “Maybe,” and if it does not agree it means “No.” Probably every theory will someday experience its “No”—most theories, soon after conception.