Dear        ,
      I’m writing to express my concern about/put forward my suggestions about .(or I’m writing to call on you to            .) I have noticed/heard that           .I’m really worried/glad about it.
      It is understandable to           ,since           .However,I think potential risks should not be ignored.The most serious/obvious risk is that           .In this sense,          .To prevent the risk from becoming a reality one day,you/we should           (or It is understandable to           ,since           .My advice is to           ,because           .If you want to           ,you should           .)
                                                                                                                                                                Yours sincerely
                                                                                                                                                                   HanMeimei