The impact of environmental Kuznets curve (EKC) effects is evaluated in the context of a full model of production and trade within and between rich and poor economies. The shape of iso-emissions curves, defined in tariff and emissions tax space, is evaluated both in the presence and in the absence of an EKC. Gains in the income of developing countries are possible without compromising on emissions where there are inefficiencies in policy. However, where policy is efficient there exists an important trade-off, evaluated here, between emissions and developing country income.