Dramatic increases in average life span in the late 19th century and 20th century, is widely credited to public health achievements, such as vaccination programs and control of many infectious diseases including polio, diphtheria, yellow fever and smallpox; effective health and safety policies such as road traffic safety and occupational safety; improved family planning; tobacco control measures; and programs designed to decrease non-communicable diseases by acting on known risk factors such as a person's background, lifestyle and environment.