Silver nitrate binds to carbohydrates in numerous tissue types after oxidation (fungus, basement membranes, reticular fibers, etc…). This is then reduced to black to visualize the tissue element desired and then section is counterstained with a contrasting dye. This solution is considered a hazardous waste. In 2009 we disposed of 3.8 liters of silver nitrate solution.  

David Simpkins who oversees lab safety, developed a method of purifying, precipitating and collecting the silver from this waste stream. The state of Washington and King County reviewed and approved this method of collecting the waste and declared it safe for reuse in jewelry or other art forms.  CellNetix is generating about 140g/year of silver. Despite increasing the volume collected 2.5 times we generated no AgNO3 waste in 2010-11.

Formalin, a 10% buffered solution of formaldehyde, is used to fix (or preserve) tissue for routine histologic analysis. With more than 87,000 specimens a year, we use a lot of formalin. In 2010 we disposed of 1,494 pounds, down from 5,229 pounds in 2009. We are now recycling about 1,800 gallons a year, about 14,890 pounds. This is analyzed, re-buffered and reused for transporting tissue cassettes and fixing tissue.

Solvents are used throughout the Histology laboratory. Xylene is a highly dangerous aromatic hydrocarbon used as a clearing agent in processing tissue and staining slides. Likewise, alcohols are used in different grades as dehydrants in tissue processing and as a solvent for various dyes. Combined annually, we dispose of 27,000 pounds. However, even in disposal, the solvent is made use of as a fuel-product off-site. As of 2010, we are recycling 1096 gallons, about 9,100 pounds of solvent for re-use at CellNetix. Together this is about 4 gallons of recycled solvent every working day of the year.

3,3 Diaminobenzidine is a potent mutagen (a chemical which can cause damage to genetic material) used in visualizing various elements in the immunohistochemistry section. As a part of our waste stream review, we targeted this chemical for waste reduction. Though we could not eliminate this as a waste stream, we were able to render the mutagenic properties of the chemical inert. This allows us to dispose of the mixed waste as a much less hazardous substance. In 2011 we will treat about 1,100 gallons of DAB.

A recent project was looking at our solid waste. One element used was paraffin. Paraffin is used in tissue processing where it replaces the water in the tissue, supporting the cells to allow the tissue to retain its morphology when we cut slides. It is reused in the processor for several weeks, but when it becomes too contaminated with solvents it will not adequately solidify and so must be replaced. Working with Northwestern Fuels, we are segregating our paraffin for them to collect. It is purified, mixed with sawdust and other byproducts of the woodpulp industry, and pressed into firestarting logs. This will divert about 7,800 pounds of waste each year from the landfill.

In June 2011, we began a program to recycle plastic containers. Mt. Baker Bio is a local Life Sciences company working to recycle and reuse plastic wastes from the medical community. They are now collecting our pipette tip boxes and ThinPrep bottles (they are compliant with maintaining patient confidentiality per HIPAA). They are also working on a process to clean and recycle our specimen bags. As a part of this process we are assessing their products, made from biodegradable plastics which decompose in the landfill in 1-10 years rather than the 100+ years of traditional plastics. Mt. Baker Bio and CellNetix are exploring what else can be recycled from our waste stream.

We now buy formalin, alcohol, and xylene in bulk 55 gallon drums. This decreases the use of our own plastic reagent containers for the decanted solutions and reduces the number of shipments coming to CellNetix. This means less fuel used in transportation and fewer “single-use” containers.