Ko tetahi waahanga tono nui o te mata kowiri tira, ko te ahumahi petrochemical, ko tenei momo kowiri tira kowiri mata he mea paerewa kounga teitei, he mea tino nui ki te tuku i te ihirangi koranu rauemi mata, te tika o te micron me te waea pakaru, te whakakore waea rua ranei.