Northwestern University laboratories utilize and generate a wide variety of hazardous substances. Appendix B contains a comprehensive list of some of the more common waste streams generated by the University. Refer to the following list for specific information:
Acids and Bases
- Collect concentrated acids and bases in original containers whenever possible. This includes nitric, hydrofluoric, sulfuric, glacial acetic, hydrochloric, sodium hydroxide, ammonium hydroxide. Hydrofluoric acid etches glass and must be collected in plastic containers. Be aware that some acids are not compatible (for example nitric acid and glacial acetic waste). Never mix oxidizing acids with organic chemicals.
- Acids and bases may be treated as the last step of a reaction. Neutralized solutions may be disposed of down a lab sink with copious amounts of water provided they are treated as follows:
- Slowly stir acid in a large amount of an ice-water-to dilute to about 5% by volume.
- Prepare a base solution of one of the following: sodium carbonate (soda ash), or sodium hydroxide. The base concentration should be 5 to 10 % for nitric and perchloric acids. A one-molar solution is about 4% (4 grams per 100 ml).
- Slowly stir diluted acid into the base solution until the pH is at least 5 but not greater than 104.
- Slowly pour the neutralized solution down the drain with large amounts of water.
3. No solvent or metal contamination is permitted for drain disposal.
NOTE: The use of chromic acid or Chromerge® is strongly discouraged by Research Safety. If used, these cleaning solutions must be collected through the third rinse. Contact Research Safety for recommendations on alternatives.
- Dispose of unused/unwanted acrylamide powder or opened liquid as hazardous waste.
- Collect acrylamide gels that contain ethidium bromide, in a lined five-gallon plastic pail.
NOTE: Only small amounts of liquid can be placed in a bag. For large amounts of unpolymerized acrylamide liquid use a container.
If completely empty and punctured, aerosol cans may be disposed of as trash. If contents or pressure remains, dispose through Research Safety.
Aqua regia is typically a 3:1 mixture of Hydrochloric Acid (HCL) and Nitric Acid (HNO3). It is commonly used to remove metals and trace organic compounds from glassware, as well as noble metals from some substrates.
Aqua regia MUST be prepared in a fume hood.
Proper PPE must be worn while making or handling aqua regia. This includes a lab coat, face shield, safety glasses, neoprene apron and neoprene gloves.
Preparation and Handling
Aqua regia should be made fresh before use; it should never be stored. Aqua regia should only be prepared and handled in clearly labeled glass containers (preferably Pyrex) inside of a fume hood free and clear of all chemicals. When preparing aqua regia, always add the nitric acid to the hydrochloric acid. The concentration of nitric acid must never be over 38%.
Aqua regia is an oxidizer, and will oxidize over time; this will form toxic gases, such as nitrogen dioxide and chlorine. Therefore, aqua regia should be disposed of as soon as possible after use. Aqua regia should never be handled outside of a fume hood, and should never be tightly capped. Aqua regia should only be handled with PTFE or glass implements. Aqua regia can corrode and react violently with metal.
Allow aqua regia solution to cool in an open container, preferably overnight, in a working fume hood. Place a sign on the fume hood alerting people to the hazard. You should neutralize aqua regia before disposal, according to the procedure below. Once the aqua regia is neutralized, submit for disposal.
- Inside a fume hood, place the neutralization container in a secondary container onto a stir plate. The neutralization container must be glass, free of any organic residue, large enough that the dilution water and aqua regia is no more than 2/3 of the total volume of the container. The amount of solution water needed is 7.5 times the amount of aqua regia.
- Weigh out the necessary amount of magnesium hydroxide (0.53 grams per mL of aqua regia).
- Add the total necessary volume of dilution water to the neutralization container, and begin stirring with a PTFE coated stir bar without over-agitating the water.
- Add the magnesium hydroxide and a dash of bromothymol blue solution to the beaker. The bromothymol solution is prepared with 0.8 g of bromothymol blue, 100 mL of water, and a drop of NaOH.
- SLOWLY add the aqua regia to the full volume of water, carefully avoiding overheating. The bromothymol blue indicator will turn yellow if you overshoot neutral pH. If your solution turns yellow, but there is still undissolved magnesium hydroxide, let the solution stir longer to equilibrate. Test the pH using a pH strip, and add more magnesium hydroxide if necessary.
- Allow solution to cool to room temperature before moving the container, capping the container, or transferring the solution.5
Once the solution has cooled, it may be transferred to another glass container for pickup. Use a pressure-venting cap. Label the waste bottle appropriately, and submit a pickup request immediately. Do not try to combine multiple batches of aqua regia solution into one waste container; Research Safety Hazardous Waste Services will pick up multiple containers.
Liquid wastes6 containing more than 5mg/L are regulated. List all arsenic bearing compounds on the chemical waste label.
Wet asbestos containing lab ware and bag them up for disposal through Research Safety.
See sodium azide.
Liquid wastes7 containing more than 100mg/L are regulated. List all barium bearing compounds on the chemical waste label.
Liquid waste8 containing more than 0.5mg/L are regulated.
Bromine Solution Waste
Bromine solutions containing more than 1% bromine must be collected in containers no larger than 1 gal. List all bromine bearing compounds on the chemical waste label.
Liquid wastes9 containing more than 1mg/L are regulated. List all cadmium bearing compounds on the chemical waste label.
Chemical Carcinogens and Mutagens
Discard in original or closed container. Bag up associated contaminated disposable labware. Triple rinse empty containers and collect all rinsate as chemical waste or present to Research Safety for cleaning.
Liquid wastes10 containing more than 6mg/L are regulated.
Liquid wastes11 containing more than 5mg/L are regulated.
Chemically contaminated glass ware, pipette tips, needles, blades and sharps are collected in a puncture proof container.
Broken glass ware not contaminated with hazardous chemicals can be put in a card board container, sealed and picked up as trash.
Liquid wastes containing more than 3mg/L are regulated12.
Cyanides, nitrites and sulfides are among the most toxic and rapidly acting substances found in a chemical lab. Symptoms of toxicity occur if these materials are swallowed, inhaled or absorbed through the skin. Keep stored in locked and secure locations away from acidic materials. Always use secondary containers to help prevent breaks or spills. Wastes containing more than 5ppm (5mg/L) are regulated13.
Dioxane (1,4-Dioxane) is a highly flammable liquid and can form potentially explosive peroxides upon long exposure to air. Containers of dioxane must be dated when opened and tested periodically for the presence of peroxides. If old, undated dioxane is found, do not open. Contact Research Safety immediately.
The range of substances that can be potentially hazardous is enormous. Almost any substance can be a hazardous waste if it is disposed of in large quantities or in high concentrations. Federal and state hazardous waste laws permit laboratories to dispose of small amounts of some chemicals in quantities that do not pose a hazard to human health or the environment. It is the policy of Northwestern University to prohibit the drain disposal of all potentially hazardous chemicals and take a more conservative approach when confronted with a less defined disposal situation.
Suitable for Drain Disposal (See Appendix C)
NOT Suitable for Drain Disposal
- Inherently toxic, malodorous or lachrymatory chemicals
- Solutions containing heavy metals
- Flammable liquids (flash point < 140◦F) of any type
- Organic solvents—methanol, acetone, hexane, chloroform
- Paint and paint thinner
- Poisons, carcinogens, teratogens or embryotoxins
- Toxic dyes and stains
- Sodium azide
- Strong acids and bases (outside of pH 5-10)
- Chromic/sulfuric acid cleaning solutions
- Photographic fixer
- Motor oil, gasoline, degreasing solutions, antifreeze or other automotive fluid
Drugs and Controlled Substances
Ether is a highly flammable liquid and can form potentially explosive peroxides over time. Containers of ether must be dated when opened and tested periodically for the presence of peroxides. Ether cans have expiration dates on the label. Dispose before they expire. If old, undated ether is found, do not open. Contact Research Safety immediately.
Ethidium Bromide (ETBR) & Propidium Iodide
Dispose ethidium bromide staining and running buffer solutions in a closed container. For the collection of acrylamide gels that contain ethidium bromide, dispose of in a lined five-gallon plastic pail.
Never use bleach to treat EtBr wastes. This actually increases toxicity.
NOTE: SYBR Safe® is sold as a safer alternative to Ethidium Bromide. It is less toxic and the stain and gels can be disposed as regular waste. SYBR Safe can be used in the same manner as solutions of EtBr. Tests indicate that it is just as, if not more sensitive than EtBr. It can also be read in the same manner with a standard UV or visible light trans-illuminator, or laser based scanner. SYBR Safe is provided ready to use as a concentrate, it can be cast directly in the gel or used as a post stain. It may also be used to stain RNA in gels. Recommended storage time is six months at room temperature.
- Unwanted or unused formalin or formaldehyde must be disposed through Research Safety.
- If you have a large number of specimens preserved in formalin that you wish to dispose of, contact Research Safety to discuss disposal options.
NOTE: The use of so-called "cold sterilants" such as Cidex® or other higher molecular weight aldehydes such as glutaraldehyde is strongly discouraged for both occupational and environmental reasons.
Formamide must be collected. If radioactive, attach a Research Safety Radioactive Waste Label and dispose of as radioactive waste.
Compressed gases are among the most problematic wastes to handle and dispose. Rent gas cylinders if at all possible so cylinders can be returned to the gas vendors if empty or not routinely used.
Lecture bottles can be a serious disposal problem. If at all possible, return these to the manufacturer or supplier for reuse. If not, dispose of through Research Safety. Label integrity is essential. Ensure that the label on each cylinder is legible. Keep the valve protection cap on the cylinder when not in use. When the cylinder is in use, keep this valve cap near the cylinder so that it does not get misplaced. Return gas cylinders to Lab Gas Services using the online tool at http://nugastanks.com/.
NOTE: Never dispose of hazardous gases by releasing outdoors or in a fume hood.
Gloves, Papers, Cardboard
Bag up gloves, papers, or cardboard that are grossly contaminated or were immersed in hazardous chemicals. (See also Hazardous Waste Supplies)
Dispose gloves, papers or cardboard that are not contaminated with hazardous chemicals, radioactive materials or potentially infectious agents as trash. See Appendix C.
Any piece of scientific equipment must be carefully surveyed and decontaminated when it may have been in contact with potentially hazardous biological, chemical or radioactive materials.
See Laboratory Equipment Disposal Form or enter a request through the NSIS Hazardous Waste Disposal module.
Solid wastes14 containing more than 5ppm lead are regulated.
Liquid wastes containing more than 0.5ppm (0.5 mg/L) lead are regulated15.
Sometimes closed primary containers may not be sufficiently odor tight. Bag or put in secondary container malodorous containers such as thiols, mercaptans, phenol/chloroform and sulfides.
Mercury and mercury compounds are especially hazardous. If spilled, elemental mercury in cracks of lab benches or floor tiles may pose an exposure hazard for years. Few hazardous waste facilities accept mercury. Therefore, it is essential that the use of mercury be avoided. Substitute mercury thermometers with non-mercury alternatives or electronic devices to measure temperature and pressure.
Solid wastes16 containing more than 0.2 ppm must be disposed through Research Safety.
Liquid waste containing more than 0.5ppb (0.0005mg/L) are regulated17. For mercury spill kits or spill response assistance, contact Research Safety.
See also Fluorescent light bulbs for clean-up of broken bulbs.
Naturally Occurring Radioactive Materials (NORM)
NORM refers to all radioactive elements found in the environment where human activities have increased the potential for exposure compared with unaltered situation.
Chemical compounds containing NORM are mostly purchased as staining agents for electron microscopy. Common compounds contain long-lived radionuclides such as uranium and thorium. Typical commercial forms include samarium, uranium oxide, uranium fluoride, uranium nitrate, uranium acetate, thorium oxide, thorium fluoride, thorium nitrate and thorium acetate.
In general, all chemical compounds containing NORM must be collected and disposed of as radioactive waste. Uranium nitrate and thorium nitrate are considered radioactive and oxidizers, and are treated as “mixed waste”.
Never mix aqueous uranyl acetate with other staining compounds such as lead citrate or other heavy metals, solvents and other hazardous chemicals.
All liquid and solid radioactive waste must be accumulated in properly labeled containers provided by Research Safety- Health Physics Services.
Liquid waste containing more than 10 ppm (10mg/L) are regulated18.
Many reported waste container ruptures and explosions in laboratories involve the accidental mixing of nitric acid with reducing agents (e.g., organic compounds). Avoid creating nitric acid waste mixtures with acetone, acetic acid, acetic anhydride, alkali metals, cyanides, aldehydes, powdered metals organic materials, ammonia, acetonitrile, alcohols, acrylonitrile and organic matter. Nitric acid is a powerful oxidant and reacts violently, sometimes explosively with liberation of toxic nitrogen oxides. Oxidation is invariably accompanied by more or less gas evolution, usually capable of rupturing closed vessels.
Uncontaminated instrument and machine oils such as centrifuge, diffusion pump and vacuum pump oils must be collected in plastic containers and labeled with a Research Safety Chemical Waste Label. Oils found in X-Ray machines and other similar devices may contain PCB's (polychlorinated biphenyls), especially if the equipment is old. DO NOT MIX PCB CONTAMINATED OIL WITH OTHER OILS. Contact Research Safety if you suspect you have PCB oil.
NOTE: All vacuum pumps must be emptied of oil prior to disposal. If sending them out for service, they must be rinsed and purged with clean oil. Collect rinse oil for disposal through Research Safety.
Organic Mercury (Alkyl and Aryl) Compounds
Organic mercury compounds pose special hazards in the laboratory. Under all circumstances, these compounds must be handled according to the Laboratory Safety and Chemical Hygiene Plan. Alkyl mercury compounds require prior approval from Research Safety before purchase or use. Contact Research Safety for assistance in planning, use and disposal before using these compounds.
Osmium tetroxide can be converted to a less volatile (safer) form by adding corn oil to the solution and shaking. This method takes advantage of the double bonds of the unsaturated oil to form a cyclic osmic ester. The reaction may be slow because corn oil is not readily miscible in water, but it's easy and it works.
Bag up osmium tetroxide contaminated labware or dispose in a closed container.
Paint can be a significant potential source of pollution in landfills. Dispose of all oil based paints through Research Safety. Old, unwanted full cans of latex paints must be disposed of through Research Safety. Opened, nearly empty cans of latex paint can be allowed to air dry until solid then be disposed in the trash as non-hazardous waste. This must be waste generated at Northwestern University. You may not bring personal wastes from home for disposal through Northwestern University.
Paint Thinner, Related Chemicals, Contaminated Rags
Chemicals associated with the use of paint thinner, brush cleaners, linseed oil, etc. must be collected for disposal by Research Safety. Rags and paper towels contaminated with paint thinner or related chemicals are chemical waste. Contact Research Safety for more information on fire rated collection containers and disposal.
Perchloric acid reacts violently with many substances. The anhydrous (dehydrated) acid presents a serious explosion hazard. It is unstable and can decompose explosively at ordinary temperatures or in contact with many organic compounds. Amounts in labs must be limited to 500grams or less. Any work with perchloric acid heated above ambient temperature requires Research Safety approval. Special wash-down hoods may be required.
Many heavy metal perchlorates and organic perchlorate salts are extremely sensitive explosives; the ammonium, alkali metal and alkali earth perchlorates are somewhat less hazardous. Mixtures of perchlorates with many oxidizable substances are explosive. Cold 70% perchloric acid is a strong acid but is not considered to be a strong oxidizing agent; however more concentrated solutions are good oxidizers. Work with >85% perchloric acid requires special precautions and should be carried out only by specially trained personnel and in specially designed fume hoods.
Peroxide Forming Compounds
Certain chemicals such as isopropyl ether, diethyl ether, dioxane, 2-butanol, tetrahydrofuran can form organic peroxides. If the solvents are exposed to air orevaporation, the organic peroxides become more concentrated. Organic peroxides may violently explode. (i.e., combined with metals or by heat, shock, friction, light or static discharge). Peroxide test strips are available through Research Safety. See the Laboratory Safety and Chemical Hygiene Plan for additional information.
Never move or open a container if crusty deposits formed on the material or its container, an oily, viscous layer appeared, or there are solids on the bottom. Immediately contact Research Safety if rusted, damaged, undated or suspicious looking containers of peroxide forming materials are found.
- Clearly and explicitly label chemicals known to form peroxides.
- Always date the container when received and when opened.
- Limit the on-hand stock to a three (3) month supply or less.
- Air dry empty containers under the hood, flush with water, deface the label and put containers in the glass disposal container.
- Store away from heat and light.
- Protect from ignition sources, physical damage, contact with strong reducing agents or oxidizers, or other contamination.
- Ensure air-tight closures on containers, purge head space with nitrogen when possible.
- Keep a minimal working inventory.
- Never store in a freezer. Use explosion-proof or explosion-safe refrigerators, as needed.
- Never store in glass bottles with glass stoppers.
- Never attempt to clean containers that were used to store peroxide forming compounds by scraping or rubbing, especially if an oily deposit or crusty residue is present.
- Test for peroxide concentration before distilling or concentrating.
- Prevention of unwanted peroxides is paramount. Stabilization and disposal can cost up to $3,000 per container.
The possession of controlled substances is only permitted with a valid Drug Enforcement Administration (DEA) license. Keep DEA regulated drugs under lock and key security until time of pick up. Any drugs provided by the Center for Comparative Medicine (CCM) must be disposed of through CCM - contact email@example.com . Dispose otherwise acquired Schedule 2-5 DEA Controlled Substances through a reverse distributor such as Pharma Logistics or acquired a Take Away envelope through Research Safety. For other drug disposal requests enter in NSIS or send an email to
- Collect liquid mixtures. Indicate percentages on the label.
- Phenol/Chloroform contaminated labware such as pipette tips and disposable pipettes with small volumes of liquid must be collected using puncture resistant container. See also Small Vials.
Phenol/chloroform waste is malodorous. Bag up gloves, wipes and empty tubes.
It is not acceptable to throw this type of waste into general trash containers, autoclave in biohazard bags, or dispose of as biological waste.
All darkrooms must be registered in NSIS with Research Safety.
Used Fixer (Black & White, Color, Bleach, Microfilm, X-ray): Used fixer solutions are classified as a chemical waste and are prohibited from drain disposal.
Stabilizers and Activators: Some activators and stabilizers pick up unexposed silver during photo processing.
Indicator Stop Bath or Acetic Acid: If Indicator Stop Bath has changed color, the solution is neutral and can be drain disposed. If the Stop Bath does not have an indicator, check the pH. Adjust the pH to between 5-10 before drain disposal. Collect Indicator Stop Bath or acetic acid solutions that do not meet either of these conditions as hazardous waste.
Developers - Black & White: In general, these solutions can be drain disposed. Identify the chemical constituents from the product's SDS and call Research Safety for disposal information.
Developers - Color: Some color developers contain hazardous constituents and others have a pH that prohibits them from being drain disposed. Identify the chemical constituents from the product's SDS and call Research Safety for disposal information and assistance.
Hypo Clearing Agent: These solutions can be drain disposed.
Mixtures: Certain photo processing operations do not allow for the collection of fixer separate from other photochemicals. These mixtures cannot be discharged to drain.
NOTE: All automated film processors must be equipped with silver recovery systems, and approved and registered with Research Safety. Conversion to digital imaging systems is strongly encouraged.
Piranha Etch Solution
There are two types of piranha etch: acid piranha and base piranha. Standard acid piranha is a 3:1 mixture of concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2).
This reaction is extremely exothermic when the peroxide is added to the acid. A standard base piranha solution is a 3:1 mixture of ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2). This mixture must be heated to 60C before the oxidizing reaction takes place.
Wear proper PPE while making or handling piranha etch. This includes a lab coat, neoprene apron, safety glasses, and neoprene gloves. Additionally, you should wear a face shield.
Preparation and Handling
Piranha solution should be made fresh before use; it should never be stored. Piranha should only be prepared and handled in clearly labeled glass containers (preferably Pyrex) inside of a fume hood free and clear of all chemicals (especially organic compounds). When preparing piranha, always add the peroxide to the acid. If the peroxide concentration is greater than 50% in a piranha etch, the solution can explode.
Piranha is used to remove residues, not actual compounds. Failure to properly remove the majority of a compound could result in an explosion, especially with organic materials. If piranha is mixed with sufficient amounts of organic materials, it will generate large quantities of heat and gas. Piranha reacts violently with most plastics and should only be handled with glass or PTFE lab ware.
Hot piranha solution should be allowed to cool in an open container, preferable overnight, in a working fume hood. A sign should be placed on the fume hood alerting people to the hazard. Once the solution is cool, it may be transferred to another glass container for pickup. This container must have a pressure-venting cap, as piranha will continue to off-gas. Label the waste bottle appropriately.
Do not try to combine multiple batches of piranha solution into one waste container; Research Safety Hazardous Waste Services will pick up multiple containers.
Chemicals that are considered reactive can react violently with air, water or other substances and also have the potential to explode. These chemicals include picric acid, sodium cyanide and sodium azide.
- Segregate oxidizers from flammable and combustible materials, organic material and reducers.
- Pyrophoric chemicals ignite spontaneously on contact with air. Store breakable glass bottles inside a plastic bottle carrier. Keep these chemicals in a glove box.
- Shock-sensitive and/or explosive materials (benzoyl peroxide) can spontaneously release large amounts of energy when struck, shaken, dropped or agitated. Some chemicals become increasingly shock sensitive with age. Inspect these regularly for degradation and dispose of promptly. Consult the Safety Data Sheet (SDS) before working with reactives.
- Never contaminate reactive chemicals with heavy metals or incompatibles.
Liquid wastes19 containing more than 1mg/L are regulated.
Liquid wastes20 containing more than 5mg/L are regulated.
Small vials filled with compatible chemicals may be collected in wide mouth quart and gallon jars or 5gal buckets with lids. Separate containers are required for the collection of mercury containing liquids, reactive, oxidizing and acutely toxic liquids. Label the outside of the collection container with all chemical contents. Choose the container size according to expected waste volumes so the container can be filled and frequently picked up for disposal.
Sodium azide is commonly used in low concentrations as a microbiocide to preserve samples. Avoid exposure to the pure material and purchase sodium azide solutions when possible. Take care not to contaminate pure sodium azide with metals or foreign materials as this can lead to the formation of explosive metal azides. Azide solutions can also form explosive metal azides in drain pipes. Collect solutions and pure material for disposal through Research Safety. Best practice is to make azide waste solutions basic >pH 10 before submittal.
Separate aqueous, halogenated and non-halogenated waste streams if possible. Halogenated solvents include methylene chloride and chloroform. Non-halogenated solvents include methanol, acetone and xylene. List all chemical constituents and the pH on the waste label. This includes any metals. Do not add excess solids or debris. Please contact Research Safety for more information on solvent recycling. Preprinted Research Fuel Blends tags are available through Research Safety for the collection of non-halogenated solvent wastes.
Collect staining solutions such as Wright's, eosin, iodine and methylene blue stains in a sealed container. List the solvent concentrations on the waste label (i.e., water, glacial acetic acid, methanol).
Universal waste is defined as a hazardous waste that is "universally generated." It has lower risk relative to other hazardous wastes. Types of universal wastes recognized in Illinois are batteries, fluorescent light bulbs, mercury containing devices, used automotive antifreeze, certain pesticides and color cathode ray tubes. A pickup request must be made within 9 months of accumulation. See Appendix D.
You may not bring personal wastes from home for disposal through Northwestern University.
Analysis and disposal of material for which the identity is not known can be expensive, from $300 to $1500 or more per unknown. If unknowns are found, consult with other workers who may have an idea as to the identity of the material. Even a general chemical classification (such as "aromatic sulfur compound") can be very helpful. A phone call to a colleague who has left will pay for itself several times over.
To prevent unknowns, remember to label all your containers regardless of size. Labeling of stock solutions is essential. All labels must include the commonly accepted name (NO CHEMICAL FORMULAS). Include any special warnings, and the date made. When scientists plan to leave the University, contact Research Safety to help clean out the laboratory so that unknowns can be avoided.
List unknown materials on the Hazardous Waste Pickup Request in NSIS. It is helpful to include the color and physical state of these materials on the form and any other information that may help in identification.
When unknowns are found in the laboratory, exercise caution as these materials may be old and unstable. If you suspect unknowns are reactive, call Research Safety prior to moving these materials.
Liquid wastes containing more than 15ppm (15mg/L) are regulated.