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Questions about dissection safety? We answer several that customers frequently ask. Topics include chemicals, volatile organic compounds, off-gassing, safety, disposal, and more.
Many people use the words "fixative" and "preservative" interchangeably. However, these solutions serve very different purposes when it comes to preserved specimens.
A fixative is initially used to "fix" a specimen's tissues on a molecular level. These chemicals halt biological processes, preventing decomposition and decay. They also stabilize the structure of tissues.
A preservative, also called a holding solution, is used to store fixed specimens. These solutions prevent bacterial growth, contamination, and desiccation of the specimens.
After fixation, specimens are then transferred to a preservative (holding solution), in which they are stored and then shipped.
Carolina’s Perfect Solution® is both a tissue fixative and preservative. Carolina developed it as an alternative to traditional formalin-fixed specimens. This fixative produces specimens with life-like color and texture, while eliminating concerns about formaldehyde exposure, hence eliminating the formaldehyde odor. Although we do not disclose the composition of this solution, independent laboratory testing confirms that it is safe and non-toxic.
The most well-known tissue fixative is formalin, an aqueous solution of formaldehyde and a stabilizing chemical, usually methanol.
Formaldehyde is a gas at room temperature. Per the United States Consumer Product Safety Commission (CPSC), exposure to this gas can cause "adverse health effects, such as eye, nose, throat, and skin irritations, coughing, wheezing, and allergic reactions." The CPSC states that "long-term exposure to high levels of formaldehyde has been associated with cancer in humans."
Many specimens used in science education are initially fixed with formalin. These include Carolina's Carosafe® specimens along with most specimens from other science education suppliers.
After reading about the hazards of formaldehyde, using these specimens may seem dangerous. However, initial formaldehyde concentration in fixatives is low, and most science supply companies use various procedures after tissue fixation, such as water baths and chemical scavengers, to minimize the amount of formaldehyde off-gassing.
At Carolina, Carosafe® specimens are initially fixed with formalin and then transferred to Carosafe®, a formaldehyde-free holding solution. This preservative is a propylene glycol solution. Propylene glycol is a common additive in foods and cosmetics. Holding specimens in this solution reduces the presence of formaldehyde, thereby diminishing or eliminating unpleasant odor.
Glutaraldehyde is another well-known fixative. It can replace formaldehyde and allows for fixation without formaldehyde, which may be dictated by school or state policy. Formaldehyde is a confirmed carcinogen—prolonged and significant exposure increases cancer risk. There has not been such a determination regarding glutaraldehyde. However, from an acute risk perspective, the effects of the two are similar.
While OSHA has not established a permissible exposure level for glutaraldehyde, the American Conference of Government Industrial Hygienists (ACGIH) has established a recommended threshold limit value (TLV) of 0.05 ppm for glutaraldehyde, as compared to a TLV of 0.3 ppm for formaldehyde. Glutaraldehyde is acutely toxic and is not without risk.
Please note that Carolina does not fix any specimens with glutaraldehyde.
Off-gassing is the release of airborne chemicals that were previously trapped in an object. These airborne chemicals are called volatile organic compounds, or VOCs.
Thousands of common products such as paints, air fresheners, cleansers, glues, and furniture release VOCs. The effects of exposure vary depending on the type of chemical, chemical concentration, and exposure time. Some VOCs have no known health effects, while others can cause minor symptoms, such as eye irritation, or even major health problems, like cancer.
To address recent off-gassing and VOC concerns, we sent preserved fetal pig specimens to an independent lab for VOC analysis. Carolina’s Perfect Solution® specimens, Carosafe® specimens, and a leading competitor’s specimens were tested in simulated dissections without ventilation.
For Carolina specimens, only two VOCs were found in measurable amounts–formaldehyde and ethanol. However, the concentrations of these chemicals were impressively low, and significantly below regulatory or recommended exposure limits.
The OSHA permissible exposure limit for formaldehyde is 0.75 ppm (measured as an 8-hour time-weighted average). Irritation of the respiratory tract can occur at 0.1 ppm. Both Perfect Solution and Carosafe® specimens had average airborne formaldehyde concentrations below 0.04 ppm with no ventilation. This level is not high enough to be detected by most handheld VOC meters.
For ethanol, the OSHA permissible exposure limit is 1000 ppm. Both types of Carolina specimens had average airborne ethanol concentrations below 5 ppm with no ventilation.
This warning was added to preserved specimen labels because of a California law referred to as Proposition 65. In California, any chemical known to cause cancer or birth defects is put on a published list that is updated annually. There are over 800 chemicals on the list. If a product contains any of them, at any concentration, the item must be labelled with a “clear and reasonable” warning label.
Formaldehyde is on California’s Proposition 65 list of carcinogens. As shown above, the formaldehyde concentrations in Carolina’s preserved specimens is significantly lower than any level of concern. However, because it is present, we must appropriately label each specimen with this warning.
Labeling only specimens being shipped to California is time and labor intensive, so we include this warning on all preserved specimens.
Anyone performing a dissection or handling preserved specimens should wear the following PPE: gloves, safety glasses or goggles, and an apron.
Immediately wash the area with water. The necessity of any further treatment would not be expected. Of course, as always, should an unexpected symptom occur, seek medical attention.
Local ventilation (e.g., fume hoods) is not required when using any of Carolina’s preserved specimens. However, some ventilation is recommended in all cases.
When using Carosafe® specimens, good ventilation is suggested to minimize formaldehyde exposure. Though off-gassing from these specimens is minimal, teacher and student safety and comfort are paramount, and compliance with OSHA regulations is crucial.
With Carolina’s Perfect Solution® specimens, formaldehyde exposure is not a concern. With both Perfect Solution and Carosafe® specimens, however, air flow in the lab increases most students’ comfort level as it minimizes the biological and chemical smells that may be present.
Carolina’s Perfect Solution® and Carosafe® specimens are not classified as federal hazardous waste nor are they biohazards. Therefore, in most cases, they can be disposed of as regular waste destined for a landfill or incinerator. Specimens should be double-bagged and sealed before being placed in the trash.
Extra holding fluids are not considered hazardous wastes and can usually be discarded down the drain into the sanitary sewer system. However, if your school or home has a septic tank system, ask an administrator or expert before you dispose of the fluids as they could upset the microbial balance that is vital to a septic system.
Although Carolina specimens and their holding fluids are not hazardous wastes or biohazards under federal and almost all state regulations, you should always check with your local solid waste or wastewater authority before disposing of them. This may mean contacting the local government office that oversees waste disposal, the local landfill, your waste disposal company, or the local wastewater treatment plant. Check with your school or university safety officer for any disposal guidelines.