By Anabelle Farnham, Communications Intern

October 13, 2021

Ever since I can remember, I enjoyed science in school because it helped me to explain the world with concrete answers. It was a way of illuminating universal truths, and providing objective views of the world….right? 

Though I have abandoned all hope of becoming a STEM major, since coming to college I have classes that challenge the ways I think about science and the weight I put into the answers “science” provides.

Most recently, I learned about something called the Threshold Theory that made me think of CHEJ. The Threshold Theory originates from Earle B. Phelps and H. W. Streeter, two engineers who developed this theory while working in the Ohio River and published it in 1958. The theory goes like this: nature, in this case a river or body of water, has the ability to absorb contamination up to a certain point. It is after this tipping point that we consider harm is being done and the “contamination” become “pollution.” This tipping point, the point when water/nature is unable to purify itself and the contamination we are putting into it becomes harmful, has been coined “assimilative capacity.”

I had not realized until reading about this theory how much I used the assumption of assimilative capacity in my life. It can not only apply to the way we consider land, but also how we consider our bodies. The EPA has set limits on many chemicals and the concentrations at which they can be released into the environment, operating under the assumption that both the environment and people’s bodies can absorb toxicity up until a certain point. 

Under this theory, the question we ask is: what is this tipping point of chemicals at which we are causing harm? However, this question assumes that all chemicals follow the same model of the Threshold Theory when this theory cannot be universally applied. 

For example, certain chemicals, such as those categorized as “endocrine disruptors” do not fit into the Threshold Theory. These chemicals can mimic our hormones, which constitute a delicate balance in our body, and can send big signals with small changes. In the case of these chemicals, a small amount can be more harmful than a large one because our body is unable to detect the difference between an endocrine disruptor or a hormone. Chemicals like these defy the Threshold Theory. 

Learning about the Threshold Theory has made me reflect more on what truths I take as givens and when these assumptions might be blinding me to something bigger. It’s not that I used to think all science is good and now I think all science is flawed; it’s that I know more clearly that the questions we ask are going to determine the answers we find. Science is a tool that we can use to help each other live healthy, full, abundant lives, but the assumptions we bring into our scientific studies will create limits for how useful science can be. It really comes down to a very basic but powerful question: What stories will we use science to help us tell?

 

Inspiration for this blog comes from Max Liboiron’s book Pollution is Colonialism, which I highly recommend if you are interested in thinking more about the way methodologies in science have the power to create or minimize harm and violence in the world.

See also A Study of the Pollution and Natural Purification of the Ohio River by Streeter and Phelps for more on the origins of the Threshold Theory

Photo Credit: David Howell/Quebec Science. Max Liboiron is an indigenous Canadian scientist who does work on plastics pollution on the island of Newfoundland.