Safety

By Richard Warburton, Ph.D.

Sterile processing professionals are exposed to many chemicals in their daily work life, including sterilant gases, disinfectants, cleaning chemicals, etc. The function of most of these chemicals is to destroy pathogenic microorganisms, and because humans share a similar biological heritage with the microbes, sterilant and disinfectant chemicals are potentially hazardous to anyone exposed.

Just as we take precautions to protect ourselves from chemical exposure in our everyday lives (e.g., turning off cars in enclosed spaces to avoid carbon monoxide poisoning), health care professionals must be aware and take the necessary precautions to avoid exposure to chemicals used in sterile processing departments.

This article discusses the health effects of the most common chemicals used in  sterile processing departments, and in particular, focuses on the long-term health effects on workers exposed to them. 

Health effects of exposure

The sterilant and disinfectant chemicals fall into several chemical groups: alkylating agents, oxidizing agents and dialdehydes.

Alkylating agents:
• Ethylene oxide (EtO) has been used as a sterilant since the 1950s and represents the gold standard for gas sterilization efficacy. Until the 1970s, EtO was considered a moderately toxic compound and the main concern was acute exposure and flammability.

The Agency for Toxic Substances and Disease Registry (ATSDR), part of the Centers for Disease Control and Prevention (CDC), reports that acute exposure by inhalation of the vapor at high concentrations leads to irritation of the eyes and respiratory system, can cause depression of the central nervous system and, in extreme cases, respiratory distress and coma. Contact with liquid EtO can freeze skin or cause delayed chemical burns.

As a result of additional studies, EtO has been classified by the International Agency for Research of Cancer (IARC) as a known human carcinogen. This chemical has been associated with leukemia, breast cancer and several other forms of cancer. It also is known to be a tumorigen, mutagen and to increase the risk of birth defects and miscarriage. A recent and uncontrolled survey by the Environmental Working Group  (www. ewg.org) found increased rates of miscarriage, certain cancers, reproductive effects, asthma and dermatitis among nurses exposed to EtO compared with nurses not exposed.

The ATSDR also states that there is good evidence that prolonged exposure to EtO has degrading effects on the central nervous system, especially in the lower extremities (neuropathy). Exposure may result in allergic sensitization with future exposure then causing hives or a potentially life-threatening allergic reaction. This response can occur with some patients who have repeated contact with EtO sterilized equipment, such as dialysis patients. Chronic exposure to EtO also can result in liver and kidney damage.

• Formaldehyde is a gas, but it is more often used in a water-methanol solution (formalin). It is both a primary irritant causing irritation to the eyes and respiratory tract as well as a sensitizer. According to the ATSDR, symptoms of acute exposure include rhinitis (irritation of nasal passages) and dyspnea (shortness of breath) at low concentrations and severe irritation of the mucous membranes, eyes and lower respiratory tract causing such conditions as bronchitis, pulmonary edema (fluid accumulation in the lungs) and pneumonia. High concentrations can affect the central nervous system, causing headache, malaise and impairment of dexterity, memory and equilibrium.

Chemical Hazards of the Workplace (5th Edition, 2004), states that the sensitization typically occurs as either bronchial asthma due to an allergic response to formaldehyde or as dermatitis.

Two forms of dermatitis are commonly observed—irritant and allergic contact. Irritant dermatitis is characterized by redness and thickening of the affected area; and in severe cases blistering, scaling and fissure formation.

Allergic dermatitis results in symptoms of itching, redness, swelling, multiple small blisters and scaling appearing seven to 10 days after initial contact by sensitized individuals. Sensitization to formaldehyde persists for life.

The ATSDR adds that sensitized individuals may experience dermatitis and asthma even at low doses, well below the OSHA permissible exposure limits (PEL) of 0.75 parts per million (ppm) and the effects may worsen for up to 20 hours after exposure and can persist for several days.

Chronic exposure can also lead to adverse effects on the central nervous system including headache, depression, insomnia, mood changes, irritability, impairment of dexterity, memory and equilibrium. Formaldehyde is classified as a known human carcinogen by IARC and increases the risk of nasal cancer. As a genotoxin, women who are or may become pregnant should avoid exposure.

Oxidizing Agents:
• Hydrogen peroxide is a primary irritant; symptoms of acute exposure include irritation to the eyes, nose and respiratory system such as inflammation of the nose, hoarseness, shortness of breath and a burning sensation or tightness of the chest.

The ATSDR also cautions that inhalation of high concentrations of hydrogen peroxide vapor can result in severe mucosal congestion of the trachea and delayed accumulation of fluid in the lungs with permanent lung damage. 

Exposure to high concentrations may damage the central nervous system, causing seizures, cerebral infarction or cerebral embolism. Contact with concentrated (more than 10 percent) hydrogen peroxide solution can cause severe damage to the eyes, immediate bleaching to the skin, with longer contact resulting in severe burns and blisters.

A warning is stated in Chemical Hazards that chronic exposure to the vapors may cause partial or complete lung collapse; as well as bleaching of skin and hair. There is disagreement about the carcinogenicity of hydrogen peroxide—the American Conference of Governmental and Industrial Hygienists (ACGIH) classifies it as a known animal carcinogen with unknown human effects, whereas the IARC classifies hydrogen peroxide as noncarcinogenic.

• Ozone is a primary irritant. Patty’s Industrial Hygiene and Toxicology (5th Edition) notes that ozone readily penetrates the upper respiratory tract and acute exposures above 0.1 ppm can result in cough, substernal pain and shortness of breath.

Concentrations up to 1.2 ppm can result in loss of cilia in less than four hours of exposure along with drowsiness, extreme fatigue, dizziness, inhibited concentration and pulmonary edema.

Prolonged exposures of monkeys to 0.2 to 0.8 ppm ozone (OSHA PEL is 0.1 ppm) resulted inflammation of the bronchioles, and irreversible formation of lesions in the lungs.

Exposure to more than 1.2 ppm may result in acute lung injury with epithelial sloughing in the airways (peeling of the lining of the cells of the lower bronchi), perivascular cuffing (lymphocytes or plasma cells in a dense mass around the vessel) and hemorrhagic pulmonary edema. Exposure to 3 to 12 ppm (the National Institute for Occupational Safety and Health’s  Immediately Dangerous to Life and Health level for ozone is 5 ppm) can be fatal with pulmonary edema and hemorrhage.

It also has been found that exposure to ozone increased the susceptibility of respiratory bacterial infections. Ozone is known to cause chromosomal damage in plant, animal and human test cells and to have caused neonatal deaths and body abnormalities when pregnant mice were exposed. Even though ozone is known to be a mutagen, there is no firm evidence that it is carcinogenic and it is classified as noncarcinogenic by the IARC.

• Peracetic acid is another primary irritant and is very corrosive to the eyes, skin and mucous membranes. Risk Management for Hazardous Chemicals (1997) states that inhalation can result in irritation to the respiratory system, including coughing, dyspnea, congestion, tightness in the chest and pulmonary edema, which may not show for up to two days after exposure. Skin contact causes redness, painful swelling, blisters and burns depending on concentration and contact time.

Few health studies have been conducted with peracetic acid and little is known about the effects of chronic exposure. Repeated exposure to peracetic acid can cause rashes, liver or kidney damage and occupational asthma.

It is not known if chronic exposure to peracetic acid will cause permanent lung damage, but in view of the similarity of its properties with hydrogen peroxide, it is a likely outcome, especially since peracetic acid is destroyed at a much slower rate by the protective catalase enzyme than hydrogen peroxide according to an article in a July 1980 issue of Journal of Biological Chemistry.

As with hydrogen peroxide, Chemical Carcinogens (1976), states that low levels of peracetic acid have been found to be a cilia toxin and mucous coagulating agent, thus inhibiting removal of lung contaminants. Patty’s reported that peracetic acid is a potent promoter of skin cancer in mice exposed to dimethylbenz-[a]anthracene, a known carcinogen (the significance to human health is not known).

Dialdehydes:
• Glutaraldehyde is a primary irritant and Risk Management reports that it is highly irritating to the eyes, mucous membranes and respiratory tract, causing such conditions as nose bleeds and difficulty breathing. It also can cause headaches and nausea. Contact with the liquid can cause damage to the eyes and brown staining to skin. Prolonged exposure can result in liver damage. Glutaraldehyde is also a sensitizer, can cause dermatitis (skin allergy and chronic eczema) and sudden asthma attacks with difficulty breathing, wheezing, coughing and tightness of the chest. It is known to be a mutagen and a teratogen and is suspected of causing cancer in animals. In the Environmental Working Group survey, nurses reported that those exposed to glutaraldehyde suffered from higher rates of allergies, asthma, anemia and bronchitis than nurses not exposed.

Patty’s reported that in a simulated study of a 12-minute cold sterilization procedure with a 2 percent aqueous glutaraldehyde solution, the operator was exposed to an average of 0.38 ppm, well above the ACGIH ceiling of 0.05 ppm; and the operator suffered severe irritation to eyes, nose and throat.

• o-Phthalaldehyde (OPA) is being widely adopted as a safe replacement for glutaraldehyde as a high-level disinfectant. OPA has the advantage that its vapor pressure is much lower than glutaraldehyde and thus the risk of adverse exposure via inhalation is reduced. OPA is still a primary irritant to eyes and mucous membranes, but contact with the 0.55 percent solution used for disinfection usually only stains skin. Advanced Sterilization Products, the manufacturer of Cidex OPA, however, reports that OPA is a sensitizer and so may elicit an allergic response. There have been few studies testing the health effects of OPA compared with glutaraldehyde. But since both molecules are dialdehydes, it is likely that OPA’s acute and chronic toxicities are similar to glutaraldehyde.

Regulations that protect

OSHA has developed regulations to govern the safe use of potentially hazardous chemicals in the workplace and for many gases and vapors, it has issued permissible exposure limits (see Table 1).

For several compounds known to be carcinogenic, OSHA promulgated a series of chemical-specific regulations including standards for ethylene oxide and formaldehyde. The ACGIH issues threshold limit values, which provide industry standards for workplace exposure.

Safety measures

The following are appropriate safety measures that should be taken to allow for the safe use of sterilant and disinfectant chemicals:

Engineering controls: Sterilant gases pose a risk because they are used in gas or vapor form and if released would present an immediate inhalation hazard. Therefore, EtO sterilizers are required to have a dedicated exhaust system and a similar system is recommended for other low-temperature gaseous and liquid sterilants and high-level disinfectants.

Continuous gas monitoring: Gas or vapor sterilizers, like any complex equipment, can fail and leaks into the breathing zone can occur. Continuous gas monitors are commercially available to warn of potential exposures for all of the sterilant gases and for most of the liquid sterilants/disinfectants. Many facilities use badges, but badges provide only a retrospective view, providing data of what the person has already been exposed to, and thus don’t give proactive alerts to prevent employee exposure.

Personal protective equipment (PPE): Use of correct PPE is vital for the safe use of chemical sterilants and disinfectants. Manufacturers of the sterilizers and disinfectants provide information on when PPE should be worn and the appropriate types of PPE needed.

Work practices: It is important for managers to ensure that the best procedures are being employed in sterilization and disinfection processes, and that they are periodically reviewed. Good work practices can reduce the risk of exposure, for example, pausing a moment until the gas monitor by the sterilizer door indicates that the gas concentration is safe before unloading the sterilizer.

Employee training: This is crucial for a safe work environment and also is a legal requirement of OSHA. Employees must understand the regulations, hazards of materials they use, the risk and symptoms of exposure, how to work safely and know the appropriate response in event of an exposure.

Moving forward

All chemicals used in sterile processing for disinfection and sterilization present potential short-term and long-term hazards to workers using them. Employers are required to ensure a safe work environment, and when the proper protocols are followed, these chemicals can be effectively and properly used by sterile processing employees on a daily basis. 

Table 1

Time weighted average (TWA); short-term exposure limit (STEL); TLV (calculated as 8-hr. TWA); Ceiling (C); American Conference of Governmental and Industrial Hygienists (ACGIH); Permissible exposure limits (PEL); Parts per million (ppm)
Source: ChemDAQ Inc., 2008s

Table 2

International Agency for Research of Cancer (IARC): 1=Known; 2A=Probable; 2B=Suspected;  3=Not a human carcinogen; N=not listed or no data American Conference of Governmental and Industrial Hygienists (ACGIH): A1=Confirmed human; A2=Confirmed animal; A3=Confirmed animal, unknown relevance to humans; A4=Not a human carcinogen; N=Not listed or no data; Registry of Toxic Effects of Chemical Substances (RTECS)
Source: ChemDAQ Inc., 2008

This article first appeared in the February 2009 issue of Materials Management in Health Care.

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