John Brian Shannon

But the science behind this paper (http://www.sciencedirect.com/science/article/pii/S0025326X12001804) is extremely hazy. They cite another paper (http://www.sciencedirect.com/science/article/pii/S0048969702000645) which measured North Sea concentrations of caffeine between 5 and 15 ng/l. Without scale, it is impossible to tell what that means. The North sea has an area and average depth of 7.5×10^5 km^2 and 0.095 km respectively- about 7×10^4 cubic kilometers, or 7×10^16 liters. At 10 ng/l, that’s 7×10^6 grams, equivalent to about 7×10^5 kilograms of coffee poured directly into the ocean. The whole world produces 8×10^9 kilos of coffee (along with 4×10^9 kg of tea) every year, so it’s entirely conceivable that such an amount could be discharged. However, the study does not take into account for the rate at which, if at all, it is biodegraded. Clearly, from coffee and tea alone, the amount going into our drains (and toilets) is far larger than what is measured.

Furthermore, they measured up to 8 ng/l in their *control* samples. Rather than attempting to more aggressively control for contamination (or method error, a much more plausible reason) they simply report values under this level as “not detected”. I personally would argue that they may have a contamination problem on their GCMS injector port before I made the field samplers wear moonsuits to work.

I would agree that the bioaccumulation of waste products of our lifestyle will always present an environmental challenge- but that challenge is a factor of the large numbers of people on the planet. It’s not as simple as “chemicals in” meaning the same thing as pollution. The extent to which coffee is or is not biodegradable needs to be factored.

We are not “caffeinating the oceans” as the title implies- we just have a poor idea of the scale of human impact on the planet. Caffeine is exceptionally easy to detect, not least of which because it is a digestion product of DNA in the coffee and tea plant, and DNA bases and their metabolites are easily detected. There’s no doubt that it has an impact on our world. But we’ve been “caffeinating” our streams and lakes for hundreds, if not thousands of years. It’s worth noting that scientists can detect evidence of our behavior, but we need much more research to figure out what that has meant in the past, and what it means today.

-Matt Harbowy