Lumping anti-vax conspiracy theories together with pioneering research in an emerging field (e.g. microplastics research), strikes me as careless.
Most people understand that vaccines are overwhelmingly beneficial and that avoiding them is bananas. I would consider this common knowledge. It's not like the public is on the fence about this that I'm aware of. A kooky subset of the population keeps demonstrably false conspiracy theories clinging stubbornly on by refusing to acknowledge material facts, but I don't think the average person finds their arguments compelling.
Micro/nano-plastics research, on the other hand, is still a virgin field of research. Until like two years ago, it wasn't really on anyone's radar. Even now, two years in, the existing body of work is still too small to be drawing any sweeping conclusions, but the data does seem to indicate a link between, say, endocrine-disrupting chemicals (e.g. pthalates) leached from everyday plastics (such as water bottles, kitchen plastics, PVC pipes, etc) and health problems such as metabolic disorders, chronic obesity, diabetes, hormonal imbalance, infertility, lower sperm counts, behavioral issues in minor children, serious birth defects, some cancers, cardiovascular diseases, etc.
I understand your contention is that if certain "toxins" (like microplastics) really were unsafe, it would be obvious by now since literally everyone is exposed to them. Meanwhile, cancer rates among adults under the age of 50 are skyrocketing at alarming rates globally. Obesity is a rampant public health crisis specifically in wealthy, developed Western nations and no one knows for certain what's driving it. There are theories, but nothing conclusive. That's why there are a lot of fad diets but no known cure for obesity that works for everyone long-term, or even for most people.
Just like people in the Middle Ages were unaware that diseases are caused by microbes invisible to the naked eye, we too may simply be attributing our public health crises to the wrong things. Micro/nano-plastics may be directly to blame for a plethora of modern health concerns. If that's the case, the fact that we haven't figured this out yet is not the same thing as us having actual evidence that micro/nano-plastics are broadly harmless.
right; I'm not making the claim that microplastics definitely have zero effects, or that we should halt research into them.
but I am making the claim that these sorts of risks — microplastics included — receive attention from lay people far outweighing their actual danger; and that a similar model of social exposure explains similar outcomes
let me draw an analogy to the microbes case: now that we have the scientific method, we can evaluate hypotheses like "failing to wash your hands before surgery causes a higher risk of infection", or "regions with stagnant water have higher cases of disease than regions with fresh water", or "a culture in which people frequently wash their hands has lower rates of communicable diseases".
since we've had decades of exposure to microplastics, we can run similar tests. it seems that we have attempted to do this research (you likely know more about the specific issue than me, feel free to correct me on this...). I see a paper in Science from last year entitled Twenty years of microplastic pollution research which seems to show quite small effect sizes
given that, what's the worst case for microplastics? it's not zero — probably they disrupt some hormones, possibly they can act as a carcinogenic. but I'd claim it's unlikely to be a high enough material risk for lay people to invest a lot of their time into
society can still do research into the effects, just as we do research into many ideas to improve public heath
does that resonate at all? or the link to social exposure isn't that compelling (maybe something else explains irrational group behavior towards vaccines etc)? or possibly there's something specific to microplastics that means we can't observe their negative effects? or the costs of switching away from plastic is low + pro-social so we should just switch, unlike with vaccines?
Why are so many health-related anxieties related to exposures that we all encounter?
Here's a model that offers some explanation — I'm calling it the mass exposure paradox. It arises from two opposing consequences of universal exposure:
Mass exposure to something harmful would generate highly significant evidence for its harm. When billions of people use or consume something for decades without a clear epidemic of harm, it becomes strong evidence against large effect sizes. Genuinely harmful exposures — such as leaded gasoline or cigarette smoking — leave unmistakable signals.
Mass exposure boosts memetic fitness. When everyone is exposed, narratives of harm can gain cultural traction, sweeping through social networks and broadcast media.
In each case, mass exposure provided a natural experiment demonstrating safety, while its memetic fitness allows anxiety to spread and persist.
The very ubiquity of an exposure strongly implies it's safe. If billions of people have been exposed for decades yet we still debate whether any real effect exists, the effect size must be negligible or nonexistent.
Genuinely hazardous substances which had widespread exposure (lead, asbestos, smoking) show clear, undeniable population-level harm without cherry-picking studies. We can generally rely on intensive research scrutiny finding the real dangers of widespread exposures if they exist.
In contrast, if you're worried about harm from exposures, it's much more likely to come from something you're specifically exposed to — something in your town, related to your behavior, or affecting people with your genes — because we don't have nearly as much evidence on those things.
Why do these low-evidence fears flourish and persist? Precisely because exposure is universal:
So, even faint signals sustain fear precisely because everyone is involved.
There are plenty of theories on the spread of low-information issues, such as availability cascades or moral panics.
The novel thing here is that universal exposure both undercuts real risk and simultaneously fuels fear (though interested to read anything that has highlighted this previously).
With that conceptualization, we should recognize that there will be many false claims of this category and so our prior on something in this category being true should be very low.
And, unless you're a specialist in the specific area or you happen to be specifically interested, I would claim that you should dismiss most reports with these properties as suffering from this paradox.