But this is coming from human waste, how much of a filter does the human body act on heroin?
If a person puts a gram of 100% pure heroin (another good question might be how purity affects the measurements) in to their body, how much will come out the other end?
Also, from a chemistry perspective, how does water bring a solvent affect opioid molecules existing? Would the water or various things in the water break down the molecules into other non detectable molecules?
Probably the molecule does break up with a certain half life, either due to sun, or other animals metabolising it, etc. Then that 2.2 kg brick needs to be replaced once every two half-lives.
Also 1 ppq is the lower bound. I think 1 ppt is quite reasonable for many methods though, so that can multiply the limit by 1000x.
All the factors above can increase the threshold amount of opoids, but here are some factors that can decrease it substantially:
There are people who dump unused drugs in, so that needs no attenuation factor.
Also, mussels are filter feeders, and oxycodone might accumulate in them substantially more (like 1000x+) than the background.
Finally, where they collected the mussels is probably correlated with sewage drains due to ease of human access, so the effective "volume of distribution" can be way less than the 110 km^3.
All that is to say, the real statistics are in the overdose calls for opoids. The headline is still an interesting cocktail-party line, but probably should be taken as a statement just by itself.
However, it is not clear if the glucuronides would be picked up by the test. Morphine glucuronides -- particularly morphine-3-glucuronide -- can hydrolyse back to morphine. It seems that the morphine molecule is largely not destroyed metabolically; the glucuronide moiety is more like a molecular "tag" that tells the kidney to get rid of something.
What if someone flushed a bunch of it down a toilet raw, for whatever reason? Same location for concentration as excrement, and honestly makes even more sense for disposal than actually throwing it into the sound directly.
If a person puts a gram of 100% pure heroin (another good question might be how purity affects the measurements) in to their body, how much will come out the other end?
Also, from a chemistry perspective, how does water bring a solvent affect opioid molecules existing? Would the water or various things in the water break down the molecules into other non detectable molecules?