( ( ( Isotopes ( with ( ( long half-lives ) ( such ( as ( uranium -238 ) ) ) ) ) ) ( -LRB- ( ( ( 5 billion ) ( year halflife ) ) -RRB- ) ) ) ( ( ( decay ( into ( daughter products ) ) ) ( with ( ( ( shorter halflives ) , ) ( such ( as ( ( ( ( ( radium -226 ) and ) -228 ) , ) ( which ( exhibit ( ( the ( higher ( activity levels ) ) ) ( that ( can ( be ( of ( ( great concern ) ( for ( human health ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NP (NNS Isotopes)) (PP (IN with) (NP (NP (JJ long) (NNS half-lives)) (PP (JJ such) (IN as) (NP (NNP uranium) (CD -238)))))) (PRN (-LRB- -LRB-) (NP (QP (CD 5) (CD billion)) (NN year) (NN halflife)) (-RRB- -RRB-))) (VP (VBD decay) (PP (IN into) (NP (NN daughter) (NNS products))) (PP (IN with) (NP (NP (JJR shorter) (NNS halflives)) (, ,) (PP (JJ such) (IN as) (NP (NP (NNP radium) (CD -226) (CC and) (CD -228)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VB exhibit) (NP (NP (DT the) (JJR higher) (NN activity) (NNS levels)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB be) (PP (IN of) (NP (NP (JJ great) (NN concern)) (PP (IN for) (NP (JJ human) (NN health)))))))))))))))))) (. .)))
Isotopes with long half-lives such as uranium -238 (5 billion year halflife) decay into daughter products with shorter halflives, such as radium -226 and -228, which exhibit the higher activity levels that can be of great concern for human health.
(ROOT (S (NP (DT The) (JJ long-lived) (NNS isotopes)) (VP (VBP require) (NP (NP (NNS thousands)) (PP (IN of) (NP (NP (NNS years)) (PP (TO to) (NP (NN decay)))))) (PP (TO to) (NP (NP (DT a) (JJ safe) (NN level)) (PP (IN in) (NP (DT a) (JJ nuclear) (NN reactor)))))) (. .)))