The document discusses biosafety levels and guidelines for working safely in microbiological and biomedical laboratories. It notes that between 1941-1949 there were over 3,000 laboratory-associated infections reported in the US, with hepatitis, brucellosis, tuberculosis, and tularemia among the most commonly reported. Biosafety levels 1-3 provide increasing levels of personnel and environmental protection, with guidelines for laboratory practices, safety equipment, and facilities appropriate for each level. Biosafety level 1 is suitable for agents not known to cause disease in healthy adults and pose minimal risk.