The wealth is the biggest contributor to pollution and strongly correlated to the environmental burden.
Eastern European countries had stricter environmental regulation than Western countries, especially, Czechoslovakia, Hungary, and Slovenia. Czechoslovakia and Hungary started to clean up polluted sites (1970) before the system change (at that time nothing happened in Germany or in the West).
Accepting EU environmental regulation in Hungary and Romania meant liberalization, lower standards and more opportunities for asking exemptions from legal compliance.
The environmental burden due to the less developed industry and lower GDP/capita was way lower in the East than in the West. In 1990, when the communist era ended, the heavy industry dropped, so the pollution and carbon emission dropped more than 30%, although it was below the Western one before.
I think your question relies on a failed preconception, that the transitioning countries had lower environmental standards and larger environmental burden. The opposite is the truth. There are awful consequences of a regulated society, but low environmental standards and "profit rules everything" are not among those negative consequences.
Alex, avoid prejudgment. If you are in a developed country, it is almost certain that your environmental footprint is several times larger than an Eastern European citizen's one.
In 1998 -after Kyoto agreement - I had a discussion with a Hungarian-American. I informed him that the US did not want to sign the agreement, although historically the US was responsible for the most CO2 emission and the agreement was still in their favor, limited the carbon emission to a historical value, what was 4-10 times higher per capita for the US than for Hungary and 10 times more than for India. He responded that their cars were more environmental friendly, because they had catalysator installed. :) Maaan, the West had 10 times more car per 100 people than the East. In the US, a person traveled 100 times more by car than in the East and their cars consumed 3 times more fuel/100km than in Hungary.
The wealth is the biggest contributor to pollution and strongly correlated to the environmental burden. Scientists think that this curve will change after reaching a high level of wealth. In the US, Australia, and the biggest part of the wealthiest countries the wealth is not there yet :). Maybe, the environmental burden/capita increases slower than the GDP/capita, but still both of them are going up. Besides, it had not just happened that the East polluted less because of the lower GDP. Since the profit and venture capitalists could not rule everything, the East applied better standards. Central authorities and their EXPERTS ruled the field not capitalists and politicians.
I do not know today China or Russia, but Eastern European countries liberalized their environmental regulation being in harmony with the West. Transition. :)
I have been working in the environmental protection business for 23 years, and worked with people who started 30 years before me and listened. I led a market leader environmental protection company for 5 years and we executed 200 million USD value decontamination projects. I did due diligence in the largest companies for preparing acquisition (BP, Shell, Slovnaft, INA) in Austria, Croatia, Hungary, Slovenia, Romania and worked in the US and New Zealand (12 countries altogether).
One example. In Hungary, we started to change underground fuel tanks (all filling stations have 1-5) to double wall tanks in 1998. This technology has a monitoring system between the walls, so any of the wall leaks, the operation stopped immediately (automatically), then you could empty the tank and fix the issue before a drop of fuel could contaminate the soil. At the same time, we started to implement the fuel vapor recycling system first for the truck downloading, later in all the pumps (you can see a small hole above the pistol, it sucks the fuel vapor back). I was responsible to finish the site cleanup and implement double wall tanks everywhere. We finished by 2006. At that time BP in Austria and Shell in Romania did not do anything! You have to know that without double wall tanks, after 10 years of operation, 80% of the filling stations contaminate the soil and the groundwater around. There is no single wall filling station in Hungary, but you can find some in Denmark, Switzerland, Austria and Germany.
The same is about health and safety. East Europe had stricter standards.