tosuchanextent相当于somuchitlittersupherdesktosuchanextentthateverytimesheopensit,loosebitsofpaperfalloutineverydirection.=itlittersupherdesksomuchthateverytimesheopensit,loosebitsofpaperfalloutineverydirection.that之后是结果状语从句theairpollutionissoserioustosuchanextentthatsomefreewayshavebeenputoutofuse结构上没有问题,但是意思上好像略有点累赘（so和tosuchanextent）,不过应该没事