Enviro-Pap: An Environmentally Friendly, Economical, and Effective Pap Stain

Pap staining consumes substantial volumes of expensive alcohol and xylene. Xylene disposal adds expense. Enviro-Pap uses environmentally friendly, inexpensive, alternative liquid solutions. Post-OG/EA 95% ethanol baths are replaced by 0.5% acetic acid (HOAc), and Scott's bluing agent is replaced by tap water. Water-scavenging aluminosilicate beads are added to xylene that is filtered daily and reused indefinitely. The Pap stain results are comparable to those produced when a chemically defined bluing agent and post-OG/EA 95% alcohol rinses are used: blue chromatin, yellow to orange keratinized cytoplasm, orangish-pink to red superficial squamous cells, RBCs, and cilia, and green cytoplasm of all other cells. To prevent blockage of eosin uptake by orange G, staining time in OG must be limited to 5–15 sec and staining time in EA must be sufficiently long (6–8 min) to permit eosin to displace orange G where expected. Using Enviro-Pap can substantially reduce a laboratory's annual staining reagent purchase and xylene disposal costs. Enviro-Pap can be implemented in any cytology laboratory; its key solutions can be extended to use in the histology laboratory as well. Assuming the laboratory is using effective OG and EA stains, the only observed potential pitfall is overstaining in OG, which can be prevented by carefully limiting the staining time and moving racks of slides quickly from OG into the first 0.5% acetic acid rinse.