A very good question. As apex predators it is reasonable to think that toxins / heavy metals / forever chemicals would be found and perhaps accumulate in snakes (and lizards). Bio-toxins are known to accumulate in muscle tissue of some turtles, especially box turtles in North America from consumption of poisonous mushrooms. Crocodilians also accumulate environmental toxins and heavy metals.
https://www.osti.gov/etdeweb/servlets/purl/20311590
The term “reptile ecotoxicology” is frequently used in this field of study.
A quick literature review indicates increasing interest in recent years of using reptiles in environmental contamination studies as valid biomarkers. Readers can do online search and find many recent and ongoing studies in this area of environmental contamination analyses. Typically, contamination in animals is done during necropsy and samples from liver and kidney are often utilized. The literature I reviewed for this response indicate adequate sampling in reptiles can be done without killing the animal by taking scale(s) and/or small needle biopsy. Still, liver and kidney tissue often remain the preferred contaminant sites for research.
The question ponders if snakes can excrete or “get rid of toxins” absent sweating mechanisms. I am not a veterinarian – perhaps one will jump in here – but snakes excrete via two physiologic mechanisms and reptile vets take this into account when, for example, injecting antibiotics. This might have pertinence to how contaminants might be excreted by snakes.
There is evidence that “many” or “most” toxins accumulated by snakes move to the skin and are eliminated by shedding. Study in New Jersey northern pine snakes:
https://pubmed.ncbi.nlm.nih.gov/1536...o%20the%20skin.
This 2021 Australian study of metalloid contamination in the western tiger snake (Notechis scutatus occidentalis) indicates that metals accumulate in scales via binding with the keratin. Would seem to confirm the above pine snake study of an excretion route.
https://www.sciencedirect.com/scienc...69749121001251
In my brief literature review I did not find a snake report of amount “skin excretion vs liver / tissue retention” of contaminants. Reptile ecotoxicology is a very recent field of study and while many reports exist; there remain many more voids in understanding the issues.
Overall report from the University of Tennessee:
https://www.researchgate.net/publica...nakes_A_Review
Savannah River Station:
https://thekeep.eiu.edu/cgi/viewcont...ontext=bio_fac
“Brown watersnakes (Nerodia taxispilota) as bioindicators of mercury contamination in a riverine system”
https://pubmed.ncbi.nlm.nih.gov/33038814/
If you read only one of these references, the following may be the best for gaining a lot of insight. For example, water dwelling snakes accumulate more mercury than arboreal and terrestrial snakes (e.g. water snakes, moccasins). In the Everglades, Burmese pythons have a higher load of mercury than non-predator fauna. Virginia water snakes accumulate more mercury than snapping turtles in the same waters. Reference to, and a number of other studies, in this paper indicate low maternal transfer of mercury to live birth and to eggs and did not seem to negatively affect reproduction or egg viability. This paper also indicates snakes do not have to be euthanized for toxicant studies. And more info.
http://www.tuberville.srel.uga.edu/d...es_mercury.pdf
However – I think the context of the question relates to pythons being a potential human food source. I did not find comparisons of muscle contamination in snakes versus that in mammals (and fish) which are common food sources (meaning, agriculturally bred cattle, pigs, chickens, catfish, and so forth). It is my opinion that under captive conditions, one could raise pythons as a human food source without any more contamination than that found in agriculture produced mammal and fish species. Control the food source of agriculturally raised pythons and the meat should be “as clean as a steak or pork chop”.
These studies also have important relevance to what and how reptile keepers feed their captive animals. Rodents raised on proper and uncontaminated diets are best. Keepers with species such as king cobras might consider whether or not to feed wild caught snakes to their kings. Keepers with large boids might consider whether or not to feed wild rabbits to their snakes. Or feed wild caught fish to their water snakes. And so forth.
Reptiles also accumulate radioactivity which can be used for environmental monitoring. I previously reported in FC about turtles accumulating radioactivity in their shells.