washington seven democratic senators urge u.s. justice department wednesday block two mergers major health insurance company say propose deal would mean high premiums lower-quality healthcare consumers department review aetna inc 33 billion plan buy humana inc anthem inc 48 billion proposal buy cigna corp. approve deal announce last july would reduce number national health insurance carriers five three urge doj justice department challenge mergers proceed prevent damage would cause competition consumers write senators richard blumenthal connecticut al franken minnesota elizabeth warren edward markey massachusetts sherrod brown ohio dianne feinstein california mazie hirono hawaii letter date wednesday address renata hesse head justice department antitrust division letter lawmakers say skeptical idea propose deal would good consumers company could use large size hammer good deal patients evidence overwhelmingly suggest cost save secure merge firm exercise market power pass consumers write lawmakers also disagree notion sale carefully choose assets competitor could resolve antitrust issue point past instance mergers divestitures lead high premiums competitors buy divest assets use convince divestitures require merge party succeed today give clearly fail recent past lawmakers write capitol hill say whether justice department sue stop deal aetna spokesman t.j. crawford say company plan close merger humana second half year believe combine company best interest consumers continue cooperate department justice thorough review transaction crawford say representatives anthem could immediately reach comment democratic senators ask justice department block insurance megamergers