The National Institute for Occupational Safety and Health (NIOSH) classifies hazardous drugs into three risk groups based on the severity and type of health threat they pose to workers who handle them. Group 1 contains the highest-risk drugs, including cancer-treatment medications with known carcinogenic properties. Group 2 covers non-antineoplastic drugs that still meet hazardous criteria. Group 3 includes drugs whose primary danger is to reproductive and developmental health.
These groupings exist to protect healthcare workers, not patients. Nurses, pharmacists, pharmacy technicians, and environmental services staff can absorb hazardous drugs through skin contact, accidental inhalation of airborne particles, or splashes to the eyes and mouth during routine tasks like mixing, administering, or disposing of medications.
Group 1: Antineoplastic and Carcinogenic Drugs
Group 1 is the most dangerous category. It includes drugs that carry special handling instructions from the manufacturer and are classified as known or probable human carcinogens by the National Toxicology Program or the International Agency for Research on Cancer. Most chemotherapy drugs fall into this group.
These drugs are designed to kill or damage cells, which is exactly what makes them effective against cancer and dangerous to the people who prepare and administer them. Even small amounts of exposure can be harmful. Research on one commonly used chemotherapy agent, cyclophosphamide, has established that there is no safe exposure level for healthcare workers. Chronic low-level exposure to antineoplastic drugs has been linked to hair loss, headaches, infertility, spontaneous abortions, and an increased risk of developing cancer.
Because of this extreme toxicity, Group 1 drugs require the strictest handling precautions: preparation in ventilated safety cabinets, double gloving, protective gowns, and in some cases NIOSH-certified N95 or N100 respirators.
Group 2: Non-Antineoplastic Hazardous Drugs
Group 2 drugs are not cancer treatments, but they still meet the NIOSH definition of hazardous because they exhibit one or more of the following properties in humans, animal studies, or lab testing:
- Carcinogenicity: potential to cause cancer
- Genotoxicity: potential to damage DNA
- Developmental toxicity: potential to cause birth defects
- Reproductive toxicity: potential to impair fertility or harm a pregnancy
- Organ toxicity at low doses: potential to damage organs even with minimal exposure
What separates Group 2 from Group 1 is that these drugs do not carry the manufacturer’s special handling information in their packaging and have not been classified as known or probable human carcinogens by international cancer research bodies. They are still dangerous to handle, but the risk profile is different.
Common examples include certain antiviral medications like ribavirin and zidovudine, and immunosuppressants like tacrolimus, sirolimus, and mycophenolic acid. These are drugs that many healthcare workers encounter regularly outside of oncology settings, which is why awareness of their hazardous classification matters.
Group 3: Reproductive Hazard Drugs
Group 3 originally contained non-antineoplastic drugs whose primary risk is harm to reproductive health, including fertility damage, pregnancy complications, and developmental effects on a fetus. These drugs may not pose the same cancer or organ toxicity risks as drugs in the other two groups, but they are particularly dangerous for workers who are pregnant, breastfeeding, or trying to conceive.
In the 2024 update of the NIOSH list, published in December 2024, Group 3 no longer has its own separate table. These drugs have been folded into the Group 2 table and are now identified with a special column marking them as having “only developmental and/or reproductive hazard.” The three-group concept still exists, but the organizational structure has been streamlined into two tables.
How Workers Are Exposed
Hazardous drug exposure does not require a dramatic spill. The most common routes are skin absorption and inhalation. Crushing or splitting tablets can release fine powder into the air. Opening vials, priming IV tubing, or pushing a syringe can generate tiny aerosol droplets. Applying topical hazardous drugs without proper gloves allows direct skin absorption. Even unpacking shipments of hazardous drugs can cause exposure if packaging is damaged.
Contamination is also easy to spread. If a worker touches the outside of a contaminated glove while removing it, they transfer the drug to bare skin. Eating in an area where hazardous drugs are unpacked or prepared creates an ingestion risk. Handling bedding, waste, or body fluids from patients receiving hazardous drugs is another common exposure pathway for environmental services workers.
Research on hospital workers chronically exposed to hazardous drugs has found elevated markers of oxidative stress and inflammation, both of which are associated with increased long-term risk of diabetes, heart disease, and cancer.
What Employers Are Required to Do
OSHA does not directly enforce the NIOSH groupings as law, but it uses them as the foundation for its workplace safety recommendations and enforcement actions. Under OSHA’s Hazard Communication Standard, employers must maintain a written hazard communication program that covers labeling, safety data sheets, and worker training for any chemical or drug that poses a health hazard.
Employers are required to provide personal protective equipment appropriate to the hazard level. When airborne exposure is possible, OSHA’s Respiratory Protection Standard applies, requiring proper respirator selection, medical evaluation, and fit testing. Exposure records, including workplace monitoring and biological monitoring data, must be kept for at least 30 years. Medical records related to hazardous drug handling must be retained for the duration of employment plus an additional 30 years.
The level of protection should match the risk group. Group 1 drugs call for the most rigorous engineering controls and PPE. Group 2 and the reproductive-hazard drugs formerly in Group 3 still require careful handling, but the specific precautions may differ depending on the drug’s route of exposure and the worker’s individual risk factors.