I worked hard in high school, studying chemistry, biology, and statistics text-books in weekends and holidays, knowing from a reasonably young age that I wanted to work in the environment. I also worked really hard at university, treating it like a job, prioritising marks over everything else. And yet, despite all those years of focused study, I look back on how I saw the world when I graduated my first degree and realise I had some things fundamentally wrong. That is to say, I write this blog not with any sort of disparagement towards those that might have worked very hard and are very capable, and yet have a different understanding of how chemicals work than I currently do, but with the knowledge that understanding chemical behaviour in the environment is very difficult. With that said, here are what I think the most common things people get wrong about chemicals in the environment.
1. The dose makes the poison
Graduates of environmental science probably took at least one class where Paracelsus and his principles was raised. The dose is the poison, we were taught, the concentration of a chemical dictates its harm. An example of this can be seen in most guidelines used to assess contamination, where the potential for harm to occur is considered unacceptably high if chemical concentrations are above listed guidelines. It was famously posited by Swiss alchemist Phillippus Aureolus Theophrastus Bombastus von Hohnenheim, also known as Paracelsus. He believed that “poisons came from the stars and that ‘all things are poison, and nothing is without poison; only the dose permits something not to be poisonous’”.
The Paracelsus Principle is one of those bits of science that seems to stick with people, even though it’s not really true. In fact, there are numerous examples of chemicals for which dose does not dictate the poison. Some chemicals can have negative impacts no matter the dose. Lead is an example of such an inorganic and naturally occurring chemical; benzene, an example of such a synthetic chemical.
It is also not a rule that toxicity increases with increasing chemical concentration. There’s two aspects to this. One is hormesis, where organisms benefit from exposure to low concentrations of chemical as it allows for adaptation. There’s also the non-monotonic dose response aspect, where negative chemical impacts changes sometimes exponentially with chemical concentration; sometimes in a u-shaped curve; sometimes toxicity increases, then decreases, then increases again. For some of these chemicals, toxicity is even highest at the lowest concentration. Here’s some examples of such chemical behaviour:
Examples of dose-response curves. A, Linear responses, whether there are positive or inverse associations between dose and effect, allow for extrapolations from one dose to another. Therefore, knowing the effects of a high dose permits accurate predictions of the effects at low doses. B, Examples of monotonic, nonlinear responses. In these examples, the slope of the curve never changes sign, but it does change in value. Thus, knowing what happens at very high or very low doses is not helpful to predict the effect of exposures at moderate doses. These types of responses often have a linear component within them, and predictions can be made within the linear range, as with other linear responses. C, Displayed are three different types of NMDRCs including an inverted U-shaped curve, a U-shaped curve, and a multiphasic curve. All of these are considered NMDRCs because the slope of the curve changes sign one or more times. It is clear from these curves that knowing the effect of a dose, or multiple doses, does not allow for assumptions to be made about the effects of other doses. D, A binary response is shown, where one range of doses has no effect, and then a threshold is met, and all higher doses have the same effect.
2. Scientists have it covered
How chemicals are regulated is as much a political and policy decision as it is a scientific one. There are some cracking good books that have this topic covered, with “The obesogen effect” and “Environmental risk assessment: a toxicological approach” being two of them.
The result of this need for collaboration between scientists and governments is that the guidelines and other limits adopted as measures of chemical safety are what represents a compromise between the push of companies and stakeholders vested in using as much of a chemical as possible, and those scientists and others charged with ensuring the safety of human health and the environment. A readily available example of this is the fungicide Shirtan, for which cancellation of approval for use in Australia was requested from the APVMA by the chemical’s manufacturer in 2020. This was despite decades of overwhelming evidence that the risks this chemical presented to the environment were unacceptable. It wasn’t the APVMA (i.e., the government agency) that stopped the use of this chemical; it wasn’t because of clear scientific evidence the chemical was not acceptably safe. Instead, it was the manufacturer of the chemical itself apparently bowing to pressure from concerned scientists and the public. Scientists provide advice to governments on chemicals and their safety, but the government is the one that decides how to act on that advice. Regulations represent these government decisions and not necessarily scientific advice.
3. If it wasn’t safe, it wouldn’t be available
There are four ways in which chemicals are regulated in Australia: as therapeutic goods (e.g., cosmetics, pharmaceuticals, personal care products, etc.); as industrial chemicals (think petrol or paint); as agricultural or veterinary medicines (e.g., glyphosate or ketamine); and as food residues (i.e., maximum residue limits for pesticides). These different means of chemical regulation are intended to allow for safe chemicals use.
None of these regulations prohibit the use of a chemical if it isn’t safe, however, and some do not prohibit the use of chemicals internationally considered to present an unacceptable risk of harm. For example, Australia brought in the new IChEMs regulations for industrial chemicals in Australia in 2022. Seven schedules for chemicals are defined in this regulation, with Schedule 6 and 7 chemicals being acknowledged as likely to cause serious or irreversible harm. Schedule 6 chemicals are permitted for use in Australia if commercially viable alternatives cannot be found. Few chemicals have been formally scheduled under the new regulations. However, it’s feasible that chemicals like PFOA would be permissible for use due to no good alternatives available for fighting fuel fires. PFOA use remains permissible in such scenarios even under the Stockholm Convention.
AgVet chemicals that have a reasonable potential to harm organisms are also allowed to be used in Australia and a number of these are yet to be reviewed for acceptability against current standards by the APVMA. For example, Australia has continued to permit the use of chemicals that have been banned internationally. Such chemicals include neonicotinoid pesticides, which pose substantial risk to multiple organisms in ecosystems outside those pests they are intended to kill. There are other problems with Australia’s regulation of AgVet chemicals too, but these are outside the scope of this blog.
Shutterstock image: Farmer spraying vegetables in the garden with herbicides, pesticides or insecticides
In the case of therapeutic goods, regulations require that environmental data be submitted when applications for new therapeutic substances are made with Therapeutic Goods Australia. The problem is, to my knowledge, these data are not assessed. Therapeutic goods are therefore permitted for use without any restrictions relating to environmental harm, despite multiple different examples of such harm occurring.
In the case of the maximum residue limits regulated by Food Standards Australia New Zealand (FSANZ), compliance with food safety standards is poorly enforced. Few food products are tested despite standards’ breaches, surveys are undertaken irregularly, and reporting of results takes years regardless of standards breaches.
And finally, we’re completely overwhelmed by the number of chemicals used in terms of our ability to assess them for risk of harm. Research undertaken in the last decade indicates we are being harmed by chemical exposure in ways that are decreasing our ability to have children. Which chemicals are causing this harm is not clear; so far, our science has not been good enough to figure this out.
4. If it wasn’t safe, the scientists would know
It’s my experience that sometimes those with science degrees are the worst at perpetuating this belief. I can understand why: when I was an undergrad, I revelled at the things science had discovered and all that we knew and could do. As a post-grad, my ardour for science dimmed a little as the realities of scientific practise, what was published as science, what wasn’t published, and who got to publish became apparent. But it’s taken the twenty years since I first graduated university to realise one of the biggest misunderstandings we have with science in the chemicals space: just because you try to measure it and can’t measure it, doesn’t mean it isn’t there and doesn’t mean it isn’t causing negative impacts. Furthermore, if you don’t even try to measure it, you can’t make statements about environmental safety. Let me explain this point further.
The measurement of chemicals is hard. One needs to have a specific recipe (method) for preparing samples for analysis; all the right equipment; all the right instruments; and a standard―that is something with a known concentration of the chemical you are measuring—as well as different things (matrices) in which the chemical can be measured, to make sure that you can measure the chemical the same way every time. The reality is most commercial and research laboratories can only measure tens of chemicals accurately―and remember how there are tens of thousands of chemicals used in Australia? In many cases, no one has spent the time to figure out the recipe (method) to analyse for said chemical and said chemical therefore cannot be measured. A great example of this problem is 6PPD-quinone: it took 15 years of dedicated effort and painstaking research for expert scientists to identify this chemical as the cause of massive fish-kills in North America. One could have measured a whole variety of other parameters in the water that showed it was safe to the environment; none of those parameters were the one that needed to be measured in this case.
In other cases, organisms may be exposed to multiple chemicals at a time. Scientists are only just now (i.e., in the last decade) figuring out how to assess the harm multiple chemicals present at once, despite this being the way both humans and the environment are exposed to chemicals. We seem to be ok with understanding that a chemical can cause harm, but not so good at understanding how chemicals interfere with each other to prohibit harm, increase harm, delay harm, or cause different types of harm in the ways that actually happen in the environment. The reality is that while there are plenty of scientists that work to understand these types of chemical impacts, such impacts are not currently well-considered in Australia’s environmental regulations.
5. I’ve been using it my whole life and I'm just fine
Ahhh, this old chestnut. There’s this belief that if something doesn’t die from chemical exposure then there’s no harm. There are many aspects of falseness to this claim. Firstly, sub-lethal effects can come in many forms, including behavioural changes, allergies, and reproductive challenges. Many of these effects are difficult to assess and detect by all but a few, highly skilled and experienced researchers. Moreover, I would consider these effects challenging to detect or make conclusions upon at an individual level; it’s not like we can go to the doctor and say ‘am I being negatively impacted by phthalates?’.
Secondly, the last decade has seen the discovery of evidence that intergenerational toxicity―that is toxicity caused in offspring, whether or not they themselves are exposed to a chemical―is occurring. You might be fine after exposure to a certain chemical, with the way negative impacts are manifested depending on age (developmental stage) of exposure as well as other epigenetic factors. That doesn’t mean your children or their children won’t suffer the negative effects of your exposure.
There reality is there are a variety of harmful effects chemicals can cause without killing an organism, from catastrophic changes in behaviour, to illness and poor health, through to infertility or poor reproductive success.
6. Only scientists do real science
I’ve noticed that there’s a tendency by scientists and the public alike, to dismiss the work of indigenous peoples, farmers, or others working on the land or on the street as not being reliable or scientific.
Here’s a thought experiment to highlight the problem with this thinking.
The sun rises in the east. How many times have you measured it? Have you seen the peer-reviewed literature outlining this reality? How do you know for sure the sun rises in the east if you haven’t corroborated this with a scientist? What about rain, does it really come from clouds? Does soil get muddy when wet?
In my view, the problem with western environmental science, is that its dependence on statistics and rigorous measurements means that many scientists spend the greatest proportion of their time working on a computer, in meetings, or in laboratories. It requires incredibly laborious and costly work to measure and collect samples across time and space. Very, very few scientists (I know none) spend the majority of their time outside observing and being in the environment and I don’t think I’ve ever heard a scientist say their monitoring program was well-funded.
This is a problem compounded in the environmental sciences area, I think, where factors important to the environment can’t be measured. For example, the importance of a bee species to ecosystem health; the role of noise in interrupting bird behaviour; the patterns of cicada movement in response to weather. These phenomena can be described, however, and those who live on the land are well-placed to make such observations. This is not poor science: all science starts this way, with our understanding of things improving as we increasingly measure and describe over-time.
We should also be aware of the bias in our western sciences, where famous scientists may not have made the discoveries for which they are attributed: malaria, pasteurisation, and small-pox vaccination are a few off the top of my head, where indigenous peoples, a Hungarian obstetrician, and Muslim women within the harem are now considered to have been the first to make such discoveries. In all cases, it took western white men to make these discoveries acceptable. Imagine what else might be known by non-scientific folk, if only we’d take the time to listen.