( ( A ( ( more serious ) concern ) ) ( ( is ( that ( ( ( chronic exposure ) ( to ( ultraviolet radiation ) ) ) ( increases ( ( the risk ) ( of ( skin cancer ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (ADJP (RBR more) (JJ serious)) (NN concern)) (VP (VBZ is) (SBAR (IN that) (S (NP (NP (JJ chronic) (NN exposure)) (PP (TO to) (NP (JJ ultraviolet) (NN radiation)))) (VP (VBZ increases) (NP (NP (DT the) (NN risk)) (PP (IN of) (NP (NN skin) (NN cancer)))))))) (. .)))
A more serious concern is that chronic exposure to ultraviolet radiation increases the risk of skin cancer.
(ROOT (S (NP (NP (NNP Exposure)) (PP (TO to) (NP (JJ ultraviolet) (NN radiation)))) (VP (MD can) (VP (VP (VB increase) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN pigment)))) (PP (IN in) (NP (DT the) (NN skin)))) (CC and) (VP (VB make) (S (NP (PRP it)) (VP (VB appear) (NP (JJR darker))))))) (. .)))