Complex sentence: These levels were so high that in the late 80s it was finally admitted that something had to be done: radiation protection standards were being revised, so that the levels of pollution would now be officially recognised as unsafe for human health.
Split into simpler sentences: These levels were so high that in the late 80s it was finally admitted that something had to be done. Radiation protection standards were being revised, so that the levels of pollution would now be officially recognised as unsafe for human health.