When incomes increase, does pollution decrease?

Does economic development always harm water quality or does increased income actually help reduce pollution? Researchers have been studying the question for a long time, and its answer can help communities or countries better predict their environmental futures.

One assumption is that for a while the environmental degradation of an area will increase as wealth increases, but at a certain level of income the environment will begin to recover. For water quality and air quality, scientists found data supporting this idea in country-level research, both in developed and developing countries. The Kuznets environmental bell curve (CEK) draw a hypothetical relationship between pollution and the average income earned per person in a given area.

In a recent study, Pandit and Paudel used models to examine the relationship between water pollutants in watersheds and income in the state of Louisiana to see if there is a CEK that shows possible recovery in water quality due to of increased income in the state.

Scientists focused on nitrogen, phosphorus, dissolved oxygen, and mercury to test water quality. So-called flux pollutants such as nitrogen and phosphorus (generally associated with agricultural pollution) can be reabsorbed in the environment. These types of pollutants contrast with “reserve pollutants” such as mercury, which, when released into the environment, will not disappear and will not be absorbed. Instead, they will continue to cause damage and roam the environment forever. Mercury is usually trapped in rocks and coal, but is released to the environment when the coal is burned to generate electricity or during the combustion of hazardous waste.

The authors used watershed data (including water pollution data) covering 53 counties in Louisiana over a 21-year period, from 1985 to 2006. Over the same period, they used the economic growth with per capita income, available from the US Bureau of Economic Analysis.

Because the researchers were looking at multiple pollutants, they decided to use a seemingly unrelated partially linear model (SUPLM) for the study. This model is often used in economics to combine several equations which are only related by their errors.

The results indicated that nitrogen followed a Kuznets curve, as did dissolved oxygen, meaning water quality in Louisiana improved with increased richness. Phosphorus and mercury both told a different story: Although phosphorus pollution fell when the state’s per capita income hit $ 14,000, pollution rose again after a per capita income of 17,000. $. A similar problem has occurred with mercury, indicating that mercury pollution has increased for the second time, possibly due to increased demand for electricity and energy.

The mixed results show that the factors that fix pollution are complicated, but some pollutants, like nitrogen, could be reduced by economic growth. What this study does not answer, as the authors point out, is whether this pollution automatically declined with income growth or whether it was the result of the state’s environmental protection policies. The authors suggest that a combination of these factors likely had some relationship with improving water quality.

This research did not reveal that economic growth would naturally solve pollution and water quality problems, but this growing area of ​​research will be of interest to both environmentalists and economists studying the link between industrial development. and water pollution. (Research on water resources, https://doi.org/10.1002/2016WR018655, 2016)

—Alexandra Branscombe, Freelance Writer

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