These jobs are unpopular because the pay is shit, not because people don't want to do them, the government could simply have grants/bonus program for people employed in these positions so that the taxpayer money directly funds the bettering of the society and environment around them. Besides, Japan is a good real world example that you do not need to lean on immigrant labor to stop your country from becoming "dirty"; it's one of the most ethically homogeneous countries and also one of the cleanest places you can visit.

Yeah... but aren't there many more poor people in Japan, too?