Much of economics is concerned with gods things people want, and are willing to pay for, or to work for, or make some effort to get. Economic bads are things which people don't want, which people will pay to be rid of.
Creation of goods frequently (even usually) produces economics bads, which is tolerated or disposed of. These are pollution.
Unfortunately much pollution creates a tragedy of the commons. For instance many companies may produce toxic smoke from their smoke stack. Everyone pays the cost for the pollution (smog over everything, reduced crop yields, bad health etc), but it is not in any single polluter's interest to reduce the pollution, because the difference that they would make is so low, and the reduction in their profits is so high.
Part of a free market it recognizing the problems with pollution and find solutions - forcing polluters to compensate those affected by the pollution.
A tax on pollution - which would be proportional to the severity of the pollution and to the number of people affected by it is a highly effective way of dealing with the problem.
Unfortunately many leftist conservationists simply stick to the mantra that capitalism is evil, and therefore refuse to search for, or acknowledge, economic solutions. Further, the common position that no amount of pollution is acceptable is unrealistic and hypocritical, and until they move past that belief they will have nothing constructive to offer the debate.
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