Biohazardous Waste Disposal
When we are working in a biology, microbiology or biochemistry lab, our activities often produce biohazardous waste: contaminated cell cultures, wastes from bacteria, animal blood elements, used needles or scalpel blades. Regardless of the source, we should handle all biohazardous waste with caution. Our students rely on us to guide them with safe practices and proper disposal procedures. Another consideration regarding the use and disposal of biologically hazardous lab items is the potential harm posed to our extended surroundings—to the entire school and the natural environment.
Where to start?
Biohazardous lab materials can be separated into four categories based on their dangers and disposal:
Type I: Microorganism/Pathogen Biohazardous Waste
In a microbiology or genetics labs there is always a chance of pathogen (bacteria, viruses, protozoa) contamination. We need to be aware of the dangers of potential contaminants and follow proper disposal procedures. Disposal of biohazardous wastes is regulated by various authorities including federal, state OSHA or state health/environmental protection agencies.
General precautions include the following:
- Cracked, broken or damaged items such as cell culture plates, tubes and blood-typing materials should not be used. They should be immediately placed into appropriately labelled biohazard disposal bags or biohazard waste containers.
- Biohazard waste disposal bags, biohazard waste containers and their contents need to be sterilized by steam sterilization prior to disposal to ensure that all microorganisms and other pathogens are dead. The sterilization is done using an autoclave and typical conditions are 120°C temperature and 15 psi pressure for about 20-30 minutes depending on the load density. Most disposal bags contain an indicator patch that changes color upon completion of autoclaving. Most waste containers are reusable and designed for an easy, one-step sterilization eliminating the need to remove the bag. Some states may require periodic inspection of autoclaves to ensure that they are in a good condition.
- Chemical sterilization is recommended for cell culture flasks or other related glassware that contains microorganisms and pathogens. Chemical disinfecting agents such as commercial bleach are effective at killing bacteria, viruses, fungi or algae. The concentrations and time will vary depending on the organisms. Soaking in a bleach solution that has a dilution of 1:10 with water is recommended. The length of the sterilization may vary from 6 hours to overnight depending on the contamination.
Type II: Animal or Human Biohazardous Waste
Animals are commonly used in biology labs so it is important to know how to handle biohazardous animal waste including blood, body parts, carcasses and bedding material that is used by infected animals. Biohazardous waste needs to be placed in biohazard disposal bags and autoclaved (see section above for general autoclave procedures). After autoclaving, the biohazard symbol on the bag should be defaced and the bag placed in the regular trash.
Disposing of dead specimens within 24 hours by bagging them in an opaque bag and putting in the trash (landfill) is allowed. However, there may be local rules on burying, landfilling, composting and incinerating that you should investigate before disposal.
Keeping pets in the classroom or lab can have many benefits, but pets or other living creatures should never be released into the wild. Invasive creatures could harm the environment, and native or non-invasive species could introduce pathogens to the local population. Before acquiring any organisms—animal or plant— develop a plan for long-term care.
Any material containing or contaminated with human pathogens is considered to be biohazard waste and needs to be disposed of properly. Human blood, blood products, tissue and cell cultures are examples of human biohazardous waste. They need to be immediately placed in biohazard disposal bags or containers before being autoclaved to disinfect.
Type III: Preserved Materials
If formalin or formaldehyde is used in preservation, you may be able to reduce the vapor of these chemicals by rinsing the specimens with water before using them. However, check with the local waste water treatment facility first to ensure that this is allowable. If your school uses a septic tank, rinsing chemicals down the drain is not recommended. Ensure that the ventilation system in your lab is on and functioning properly when working with preserved specimens.
Before disposing of preserved specimens, some scientists suggest additional rinsing and soaking to remove more of the preservative. I disagree with this procedure, as it adds more chemicals to the waste water which enters the water cycle more quickly. Of course, specimens that are not given a final rinse before disposal will eventually leak their preservative, but in a landfill the leakage is likely to be more contained over a long period of time.
Type IV: Sharps and Broken Glass
Sharp objects such as needles, razor blades, scalpel blades, glass pipets and broken glass are all considered biohazard waste. They must be handled with care and disposed of following proper procedures.
- Sharps Disposal: All sharp objects must be promptly disposed of in a leak-proof, puncture-resistant and properly labeled sharps container. All non-contaminated broken glass can be disposed of in the sharps disposal box. For safe handling the container should never be more than 3/4 full. Keep the container closed and securely sealed.
- Contaminated Sharps and Glass Disposal: Sharps and broken glass that are contaminated with potentially hazardous biological materials or fluids should be sterilized prior to collection and/or disposal.
Final note: Always handle biohazardous materials using Personal Protective Equipment (PPE) such as disposable gloves to prevent possible contamination.
That’s it for now. Be safe my friends!