In Belgium, pollution fees are based on measured concentration or conversion coefficients for organic matter and suspended solids, heavy metals, nutrients (N and P) and cooling water. In Mexico charges are linked with discharges’ quantity and strength (in excess of permissible biochemical oxygen demand [BOD], chemical oxygen demand [COD] and total suspended solids [TSS] levels) and with the carrying capacity of recipient bodies, which is differentiated for industrial and municipal wastewater discharges. In Hungary, the “environmental load charge” applies to all activities that require a discharge permit (e.g. wastewater companies) and takes into account both the vulnerability of receiving waters and the technologies used for wastewater treatment and sludge disposal, to strengthen the incentive nature of the measure, a rebate applies for polluters that adopt approved pollution reduction measures (pre-treatment) and fines apply for discharges in excess of permits (OECD, 2008a). In some instances (e.g. Czech Republic and Slovak Republic), revenues are collected nationally but allocated to specific national environmental funds.