In the same way that a small amount of cleaner contributes little to the water?
The comparison between industrial dumping, and a small amount of cleaner on a boat is the same. 10, 000 gallons of toxins from industrial usage is not the same. The analogy about everyone doing it applies just as well to the cleaning and small amount of copper released, except that the copper stays around longer.
Moderation and reasonable precautions are a much better solution than absolute bans based on lack of understanding of differences in scale.
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