"Appalling working conditions" can be used as a synonym for "atrocious working conditions." This term suggests that the conditions in question are truly terrible and difficult to bear. "Dreadful working conditions" is another term that is closely related to "atrocious." This phrase emphasizes the negative impact that the working conditions can have on people's lives. Other possible synonyms include "horrendous working conditions," "grueling working conditions," and "inhumane working conditions." All of these terms suggest that the working conditions are unacceptable and need to be improved in order to ensure the health and well-being of workers.