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Does Scientific Literature Still Support “The Dose Makes the Poison” Adage?

We all learned in middle school science class that “the dose makes the poison”. If a rat eats some poison, he might get sick. But if he eats a lot, he’ll die. See folks, science is simple!

For the last several decades scientists from differing fields have been debating whether or not this traditional toxicology adage still holds true, given the new research around low dose exposures to certain chemicals. So today I’d like to take a deep dive into this topic because like most things that involve science, the answer isn’t simple.

[For extra credit: I highly recommend listening to this interview with prominent scientists who discuss this topic in an episode called “The Poison Paradigm“, via Cited.]


Myth: These scientific concepts are easy to share through social media posts.

Fact:

Social media has fueled an alarming rate of scientific illiteracy because scientific concepts like the dose response curve can’t be distilled down into a graphic. What has happened appears to be both an unnecessary alarmism about certain chemicals and routes of exposures that have fueled misinformation (e.g. simplified statements such as, “preservatives are all toxic“, “phenoxyethanol is a hormone disruptor“). If you’ve been reading my work for a while, you’ll know that I shudder at absolutist statements. While easy to understand, they fuel unfair misconceptions around the field of public health science.

And on the other hand, there is now a backlash due to the misrepresentation of science, which now labels anything “clean living” as B.S. marketing, anti-science, fear mongering. As you can see, we have a problem.

Where the scientific evidence lies however, is in between the two “camps” of people evolving over the internet. Here’s the punch line:

A growing body of science shows us that “the dose makes the poison” is an over simplification of what we know to be true about chemicals and our health. This old adage misses three decades worth of peer-reviewed research showing that low dose exposure to certain chemicals (hormone disruptors or heavy metals like lead) matter. As does the timing of exposures (critical windows of development) and the cumulative impact of multiple exposure routes (communities living near industrial pollution, multiple product uses etc.)
It is also true that some low dose exposures are not of concern at all.


Myth: Scientists agree on how chemical exposures impact our health.

Fact:

Scientists have disagreed on this topic for decades, the difference now is that the debate is playing itself out with the general public, over social media platforms. Scientific debate is a normal part of the scientific process and is healthy to have different fields of science challenging each other, this is part of what helps us to evolve our understanding of diseases and how to prevent them.

The important point here is that anyone who simply states that “the dose makes the poison” as the only scientific truth, is either turning a blind eye at the full body of peer-reviewed literature or is under-educated on this body of research.


Myth: There is no reason to worry about any harmful chemicals in your household products, because “the dose makes the poison” and you’ll never be exposed to enough of these chemicals to cause harm.

Fact:

Some exposures are okay and aren’t cause for concern. Other exposures should be avoided if possible. The question remains: if you had the choice to choose between two products, one with a known carcinogen and one without, which one would you choose? If companies can make products with out toxic chemicals, why wouldn’t they?

More research shows that by removing toxic chemicals from our lives, we can reduce the amount of these chemicals in our bodies within three days. Again, where possible, why no err on the side of caution?

Finally—and this is an important point—only looking at the exposure of the person using a product in your home completely misses the rest of the product’s lifecycle. Someone can easily say that you don’t need to be worried about your exposure to a plasticizer chemical in a product in your home. But what they are missing are the other exposures to people, most often low income and communities of color, along the lifecycle. That plasticizer chemical was likely created in a petrochemical facility which pollutes the air and water and bodies of the communities who live next to that plant (these are called fenceline communities). Or the persistent water pollution that the same chemical emits when it’s disposed of and burned in a waste incinerator, again, often located in low income communities.

So while looking solely at exposures to a chemical from a product, you are missing the greater issue. How are we as a society going to shift the way we use, produce and dispose of chemicals. And when will we start to think more holistically about the impacts they have across the span of their lifetime?


Myth: The scientific literature doesn’t support the notion that small doses of endocrine disrupting chemicals are harmful.

Fact:

There is widespread scientific consensus that low doses to hormone disrupting compounds defies traditional toxicology (and it’s important to note that we have known this to be true for certain heavy metals like lead, where there is no “safe” level and other persistent, bioaccumulative and toxic chemicals (PBTs)).

The science is so robust that there are dozens scientific consensus statements on endocrine disrupting compounds. You can read them for yourself HERE. The science is solid, led by some of the brightest researchers in the world, and all of it is peer-reviewed and published in credible journals.

If you want a high level summary of the scientific consensus, check out the Endocrine Society’s second scientific consensus statement here (they are the well respected professional organization for endocrinologists). An important excerpt from this statement showcases why “the dose makes the poison” doesn’t hold true for this class of chemicals.

Low-dose and non-monotonic dose responses (NMDR) are common and challenge classical concepts of toxicology testing, such as potency, threshold, and the establishment of ‘safe’ doses of exposure during the process of risk assessment and subsequent management.

– The Endocrine Society’s Second Consensus Statement on the impacts of Endocrine Disrupting Compounds

Myth: Low dose exposure to any chemical is bad.

Fact:

With all the complexities around communicating the science of safety, many people have gone to the extreme to make decisions in their lives based on fear, unfounded in science.

For example, I have long told people not to share this non-fact floating around the internet “Did you know it only takes 26 seconds for chemicals in beauty products to be absorbed in your body?“. First, there is no evidence or study to back up the 26 seconds claim. Second, not all chemicals are absorbed through our skin (certain silicones are designed to sit on top of the skin and wash off when you wash your face). Third, just because something enters your body, doesn’t automatically make it harmful.


Myth: All chemicals are bad.

Fact:

Related to the last myth, it’s important to note that everything is a chemical and people misuse the terms “chemicals” and “toxin” all the time. Certain chemicals are toxic even at low doses (lead, mercury, certain pesticides or hormone disrupting compounds) and some chemicals are not toxic in small amounts. The converse is also true, even too much water (a chemical) can be harmful to health.


Myth: I can control all chemical exposures in my life.

Fact:

I have been using non-toxic products for almost 15 years and when I had my body tested for toxic chemicals by the Silent Spring Institute, I still had chemicals of concern in my body. This is because we simply can’t—nor should we try—to control everything that enters our bodies. We can’t live in a bubble! I am exposed to pesticides that float through the air, make their way as contaminants in my food, bisphenols lace the food I eat at a salad bars and the water I drink contains legacy chemicals of concern.

Not having complete control should not make us panic. <deep breath>

We can do two things: make the best choices we can to prevent exposures where possible. And call on our government leaders to pass legislation that makes companies avoid using these chemicals in the first place.

It’s also important to know when it’s ok to take small exposure risks through certain pharmaceuticals and medicines necessary to protect public health. For example, I needed to use a prescription after the birth of my second child that contained parabens. I took the medicine for three weeks and THAT’S OKAY.


Myth: If I use a shampoo with an ingredient that is a known carcinogen, I will get cancer.

Fact:

The development of disease is multi-factorial and can’t be distilled to a smoking gun (except where there are clear exposures from point source pollution [e.g. living by a manufacturing facility] or workplace exposures). This doesn’t discredit however the importance of removing or preventing exposures where we can.

The logic behind this myth is always baffling to me, if you have the opportunity to avoid a chemical linked to cancer, why wouldn’t you?

Myth: Doctors think “clean living” is an alarmist scam

Fact:

Many medical professional organizations (these are the organizations that doctors use as guidance for their fields of medicine) have weighed in on the importance of preventing exposures to toxic chemicals. While it is true that medical school curriculum falls (very) short of teaching about environmental exposures—only briefly covering the basics like the link between lead paint and brain development and air pollution and asthma—the professional organizations responsible for staying up to speed on the science have made strong statements in support of removing toxic chemicals from consumer products.

A few examples include:


Like most things in science, this topic takes explaining and a critical mind. Please join me in doing your part to communicate carefully around the field of environmental health sciences. And to all the haters out there, please read up on the science!

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