Once again the solution to pollution is dilution. Small amounts of many toxic substances often cause no harm and, in fact, can in some cases be beneficial to certain lifeforms. That phenomena is called hormesis. It certainly makes sense to monitor all such cleaning operations while perhaps avoiding the broad-brush legislation that lumps all operations into a single one-size fits all law.
A couple of minor errors in the previous posts worth noting. DDT was banned on the fear of it's being a carcinogen risk. In actuality, when tested on rats it has been shown to be an anticarcinogen if anything. The study on eagle's eggs was flawed in that the eagle's calcium intake was also reduced in the original study. One of the researchers in this area, J. Bitman, performed his study again without reducing the calcium in the bird's diets and found no thinning of the egg shells. Science magazine refused to publish the second study vowing that they'd never publish anything favorable to DDT. the results were enventually published in Poultry Science, not exactly the most widely read of scientific journals. A leading proponent of DDT was the late J. Gordon Edwards, professor of entomology as San Jose State University who regularly consumed a spoonful of the substance at the beginning of each year for the enlightenment of his students. He died in 2004 at the age of 85. One might think about these facts when reading about malarial deaths in the third world. Malaria regularly infects 300,000,000 people annually with nearly 2,000,000 dieing each year. The vast majority live in sub-Saharan Africa.
The drilling mud cited as containing heavy metals is most likely bentonite mud. Bentonite is a naturally occuring high-solids clay that is used in oil and gas drilling as well as water well drilling. It is used to keep the bore hole open during rotary drilling operations and also as a grout to prevent transmission of fluids in the well casing annulus. Bentonite is also fed to dairy cattle as a laxative and is also used in humans for the same purpose. Bentonite is used in winemaking and is reputed to be an ingredient in Clearisil acne cream. It's also used in some cosmetics. Bentonite contains no heavy metals. Oh, and 99% of oil and water wells are drilled and/or grouted using bentonite.
While sailors perhaps more than most care about water quality and the environment it would certainly be nice to see some data on areas where removed bottom paint has accumulated, assuming that it does indeed tend to accumulate from hull scrubbing versus dissipating, and what actual environmental effects result. One thing we do know for sure is that recovering it and concentrating it causes the production of a highly concentrated amount of heavy metals that you cannot just dump anywhere. And those new hazardous waste dumps are just popping up everywhere you turn aren't they? But then, like DDT, it's not always necessary for government to have all the facts in place before banning either a substance or a practise. A shrill cry of, "what about the children?" is often sufficient to obviate the scientific process in favor of the politically expedient, "just to be on the safe side". Unless of course, those children are African.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.