Unattended hazardous chemical waste can be unsafe, and at times, dangerous. For example, during one high school’s chemistry lab mock–Occupational Safety and Health Administration (OSHA) inspection, an acid cabinet revealed a large bottle of picric acid with crystals around the cap. Picric acid is a potential explosive, as some schools have learned the hard way. The state bomb squad had to be called in to safely remove the bottle. The chemistry teacher “forgot” it had been placed in there and basically ignored it for several years!  

In another incidence of hazardous chemical neglect, a 40-year veteran chemistry teacher retired. The newly hired first-year chemistry teacher entered the laboratory instructional space and surveyed the cabinets. In the back of the lab, the new teacher found a cabinet containing many bottles of older chemicals—some very hazardous— that the retired teacher had placed there for safer keeping and forgotten.

Determining whether a hazardous laboratory chemical should be disposed of depends on several criteria related to the chemical’s condition and regulatory requirements and the risks associated with its continued storage. It should not depend on teachers forgetting its presence or saving it for decades for a rainy day.  

Key factors to consider for an appropriate chemical disposal program include the following.

1.    Stability and Reactivity. If a chemical shows signs of degradation or instability (e.g., peroxide formation in ethers, decomposition in older unstable compounds), it may be unsafe to store and should be disposed of.
2.    Physical Condition. Signs like crystallization, cloudiness, discoloration, or the presence of sediment in a normally clear liquid can indicate that a chemical may have degraded and could be unsafe.
3.    Expiry Date. Certain chemicals have a shelf life or expiration date beyond which they may become unstable or lose effectiveness. Expired chemicals often need to be disposed of according to laboratory or institutional policies. (See Safety Data Sheets, commercial supplier resources like Flinn Scientific Disposal Protocols, etc.)  
4.    Indefinite Shelf Life. Many chemicals have indefinite shelf life and are still safer for use.  
5.   Container Integrity. Leaking, corroded, or damaged containers increase the risk of exposure or environmental release, making it critical to dispose of the chemical safely.
6.    Labeling and Documentation. Chemicals with missing or illegible labels, or those with unclear identification, are often disposed of because their identity and associated risks cannot be verified.
7.    Quantity and Usefulness. If a chemical is no longer needed for experiments, it may be safer to dispose of it than to store it indefinitely.
8.    Regulatory Requirements. Many chemicals are regulated under federal, state, or local environmental, health, and safety laws. Certain chemicals, especially those classified as hazardous waste, have specific disposal requirements, regardless of their physical condition.
9.    Storage Compatibility. If the chemical poses a hazard/risk due to incompatibility with other materials stored nearby, it needs to be relocated in a safer place. If a safer place is unavailable, the chemical should be listed for disposal to reduce the risk of accidental reactions.

By following these disposal criteria, laboratories can ensure that chemicals are disposed of responsibly, reducing potential chemical safety hazards and health and safety risks for employees, students, and the environment.

Staff in middle level and high school science/STEM instructional spaces (e.g., laboratories and classrooms) and related areas (e.g., storerooms, preparation rooms, etc.) can ensure the responsible disposal of hazardous chemicals by following a set of best practices that prioritize safety, environmental protection, and regulatory compliance. Here’s a recommended comprehensive approach.

1. Maintain an Up-to-Date Chemical Inventory. Keep a detailed inventory of all chemicals, including quantities, hazards, and expiration dates. Make sure to label all chemical containers properly including hazard symbols and expiration information.
2. Educate and Train Staff and Students. Provide annual training for science teachers and lab technicians/paraprofessionals on potential chemical safety hazards/risks, handling, storage, and disposal procedures. If possible, include chemical safety and environmental awareness in the student curriculum.
3. Follow Local, State, and Federal Regulations. Comply with OSHA, Environmental Protection Agency (EPA), and local environmental agency guidelines for hazardous waste disposal. Be aware of specific use and disposal rules for hazardous chemicals.  Make an active list of prohibited use hazardous chemicals such as mercury, formaldehyde, and others.
4. Implement a Chemical Waste Management Plan. Store incompatible chemicals separately (e.g., acids away from bases). Clearly label all waste containers with contents, hazards, and accumulation start dates. Ensure appropriate waste containers are compatible with the contents and are sealed properly.
5. Certified Licensed Hazardous Waste Disposal Companies. Contract with licensed hazardous waste disposal firms to appropriately remove and treat chemical waste responsibly. Schedule regular pickups to prevent the accumulation of hazardous materials.
6. Reduce Chemical Use and Waste. Use microscale chemistry techniques to minimize chemical quantities. Purchase only the quantities needed for the academic year to avoid stockpiling. Remember before purchasing any chemical to plan for appropriate storage, safer use, and disposal. Schools basically own the chemical from cradle to grave!
7. Encourage Substitution and Green Chemistry. Substitute hazardous chemicals with less dangerous alternatives when possible. Use non-toxic or low-toxicity chemicals in experiments and demonstrations.
8. Store Chemicals Safely. Store chemicals in designated, ventilated, and secure cabinets according to compatibility groups. Use secondary containment to prevent leaks or spills.
9. Respond to Spills and Accidents Appropriately. Keep spill kits accessible and train staff on how to use them. Report and document any incidents according to school or district policy.
10. Regularly Review and Audit Practices. Conduct periodic audits of chemical storage, usage, and disposal. Update procedures and training based on audit findings and new regulations. Make sure these best practices for chemical disposal are reflected in the chemical hygiene plan.

By following these steps, high school and middle school science instructional spaces and related areas can significantly reduce health risks and environmental impact while fostering a culture of safety, responsibility, and environmental ethics. Remember to empower students to be “lab safety officers” on a rotating basis to promote peer accountability relative to safer usage and appropriate disposal of hazardous chemicals. Finally, celebrate safer use and disposal practices via recognition programs or displays.

Submit questions regarding health and safety issues in science/STEM instructional spaces to Ken Roy at safersci@gmail.com. Follow Ken Roy on X: @drroysafersci. You can also follow Dr. Roy on LinkedIn at https://www.linkedin.com/in/dr-ken-roy-07218713/.