From Envirowiki

Social justice refers to a loose but large network of campaigns for justice for those in the world at the bottom of various hierarchies. It is usually based around and against various discriminations, most commonly racism, and economic discrimination, but also sexism, heterosexism, age, physical and mental disability discrimination. Environmental justice is a movement closely related to both social justice and environmentalism, which takes into account the fact that it is often the poorest, and non-white people who feel the brunt of environmental problems, in this global economic system.