The linkage between per capita GDP and sulfur emissions for 12 Western European countries was analyzed over a period of more than 150 years. The analysis also looked at the impact of air pollution regulations on the shape of the income-pollution relationship. At both the aggregate and country levels, we find an inverted U-shaped relationship and the estimated turning points of most countries are plausible. In addition, environmental regulations are found to lower the EKC and they can also shift the turning point of the curve. In some cases, the shift is to the left and in a few to the right.
Markandya, A., Golub, A., & Pedroso-Galinato, S. (2006). Empirical analysis of national income and SO2 emissions in selected european countries. Environmental and Resource Economics, 35(3), 221-257. https://doi.org/10.1007/s10640-006-9014-2