There are costs and benefits to anti-pollution legislation. The costs are mainly economic while the benefits are typically not economic.
The benefits of anti-pollution legislation are not easily quantified in economic terms. They have more to do with the quality of life for the people in a polluted area. When anti-pollution legislation works properly, people are more able to enjoy their lives. They do not have to worry about having their health damaged by pollution. They are able to enjoy nature. These are things that improve quality of life but are not easily assigned a value in dollars.
The costs of anti-pollution legislation are much more quantifiable. They tend to result in higher costs for various businesses. When businesses have to install scrubbers on smokestacks, for example, or when they must do other things to reduce emissions, they lose money. When the costs of compliance with environmental regulations become too high, business can decide to move to places with fewer regulations. This harms the local economy in quantifiable ways.
Because the costs of such regulations are quantifiable and the benefits are not, these sorts of laws are often very controversial.