RESUMO
A comprehensive global inventory of past, present, and future steroid emissions was firstly developed based on the global 5' × 5' grids relevant data available. From 1970 to 2070, the growth rate of the annual global steroid emission was relatively stable around 10%. At present (in 2015), the global steroid emissions was 18,270 t, with 17% contributed by humans. Almost one-third of total animal emissions have been occurring in India and Brazil. India also had the highest value of human steroid emissions. Regions with highest steroid emissions were concentrated between 10° ~ 35° N and 70° ~ 90° E. The increase of sewage treatment rates can effectively reduce the total quantity of steroids entering the environment, especially for some developing countries. But the "technology bonus" from sewage treatment process will be exhausted until to 2030. Meanwhile, global surface water pollution was predicted based on steroid emissions into water compartment and on the digital river network with annual river discharge. The modelling results show that steroids are widely distributed across the globe, with concentrations mostly below 100 ng/L. However, if no proper treatment measures for animal excretions, in another 100 years, the range of the surface water contaminated by steroids will increase by 1.2 times. The Nile River resulted as the most polluted among the eight world's longest and famous rivers during the whole period investigated. Various measured concentrations worldwide validated our modelling result. The global steroid emission inventory and surface water pollution from past to the future will stand as an important data and knowledge base for the management of pollution from different types of steroids at global and regional level.