This area is seriously contaminated with radioactive isotopes.

In this chemical reaction, a specific isotope is produced.

This rock is radioactive, so care must be taken when handling it.

His body is very healthy.

In my area, a summer festival is held every year.

This problem is very serious.

Do you understand the seriousness of this problem?

In physics, blackbody radiation is a very important concept.

Education about sex is very important.

The pollution in this area has become a serious problem.