A-----------nsw-----------er ----------- To----------- de-----------cid-----------e i-----------f t-----------he -----------Uni-----------ted----------- St-----------ate-----------s s-----------hou-----------ld -----------tri-----------m t-----------he -----------pol-----------lut-----------ion----------- le-----------vel----------- to----------- ze-----------ro -----------or -----------not-----------, o-----------ne -----------mus-----------t l-----------ook----------- at----------- th-----------e m-----------arg-----------ina-----------l b-----------ene-----------fit----------- an-----------d m-----------arg-----------ina-----------l c-----------ost----------- of----------- re-----------duc-----------ing----------- po-----------llu-----------tio-----------n a-----------nd -----------the----------- le-----------vel----------- of----------- po-----------llu-----------tio-----------n i-----------n t-----------he -----------cou-----------ntr-----------y. -----------If -----------the----------- po-----------llu-----------tio-----------n l-----------eve-----------l i-----------s s-----------ubs-----------tan-----------tia-----------lly----------- hi-----------gh,----------- th-----------en -----------cer-----------tai-----------nly----------- th-----------e m-----------arg-----------ina-----------l b-----------ene-----------fit----------- of----------- re-----------duc-----------ing----------- po-----------llu-----------tio-----------n l-----------eve-----------ls -----------wil-----------l b-----------e g-----------rea-----------ter----------- th-----------an -----------the----------- ma-----------rgi-----------nal----------- co-----------st -----------of -----------red-----------uci-----------ng -----------pol-----------lut-----------ion----------- le-----------vel-----------s a-----------nd -----------the----------- re-----------duc-----------tio-----------n i-----------n p-----------oll-----------uti-----------on -----------wil-----------l h-----------ave-----------