Histology Safety 102: The Laboratory Standard Part 1

The histology laboratory is a dangerous place to work for employees.  Sharp knives, slick floors, hazardous chemicals and bloodborne pathogens are just the main sources of potential accidents.  A way to keep histology laboratory employees safe is to provide information on dangers, explain the ways in which employees can protect themselves, and provide annual training to reinforce this information.  This is not just a good plan.  In most instances, this plan is backed by laws and regulations.  This current series of blogs will delve into the various regulations, and how laboratories need to be in compliance in order to keep employees safe.

OSHA passed “Occupational Exposure to Hazardous Chemicals in the Laboratory” in January 1990, which is known as the Laboratory Standard.  It is to be used in conjunction with the Hazard Communication Standard and Chemical Hygiene Plan to inform and train employees on the dangers of exposure to hazardous chemicals that they may work with.

Chemical Hygiene Plan

Employers were required to write and implement a Chemical Hygiene Plan (CHP) by January 31, 1991.  At a minimum, the CHP must describe work practices, procedures and policies to protect workers from hazardous chemicals.  The following elements must be part of the CHP:

  • Description of procedures and personal protective equipment (PPE) required to perform specific tasks.
  • Description of specific exposure control methods.
  • Description of methods used to confirm proper operation and function of mechanical controls (i.e. fume hoods, ventilation, etc.).
  • Identification of any procedures hazardous enough to warrant prior approval by the employee before implementation.
  • Description of employee training and medical consultations.
  • Designation of a Chemical Hygiene Officer or Committee.
  • Designation of an area within the laboratory where “select carcinogens” are handled.
  • Description of procedures for the safe removal of contaminated waste, and decontamination procedures.

Hazard Communication Standard

This “Right to Know” standard was pre-empted by the Laboratory Standard.  However, some aspects still apply.

    • Material Safety Data Sheets (MSDS) for any hazardous chemical in the workplace must be on file, and available to employees. These are now known as “Safety Data Sheets” (SDS).
    • Employers must have a written hazard communication program. Under the Laboratory Standard, the CHP takes its place.  Note that the Formaldehyde and Bloodborne Pathogen Standards require their own written programs.
    • Hazardous chemicals are required to be labeled with the identity of the chemical and the appropriate hazard warning.
    • Employees must be provided with information and training upon initial assignment and whenever a new hazard is introduced.
    • Employers must provide annual training and reviews.

Chemical Storage

The worst thing you can do in your laboratory is to store all the chemicals by alphabetical order.  Each chemical has its own characteristics, detailed in the SDS that will determine the storage conditions.  Additionally, the SDS should spell out what chemical incompatibilities exist- that is, what chemicals to not store it with. 

Chemical Storage Considerations

Light sensitive chemicals must be stored in dark containers in dark, cool storage areas.  Peroxides fall into this category, as do silver salts, dioxane, acetaldehyde, sodium iodide, mercuric chloride and mercuric iodide.  (Note- you should not have any mercury compounds in your laboratory- see theMercury section.)

Acids should be stored by themselves, in an acid cabinet away from formaldehyde, bases, alcohols and oxidizers.

Bleach is a base, composed of 5% sodium hypochlorite.  If it is mixed with formaldehyde or ammonium hydroxide, toxic gases can be released.  Bleach should also not be stored next to acids or methanol.

Flammable compounds such as acetone, xylene and alcohol should never be stored in a regular laboratory refrigerator or freezer.  These chemicals can vaporize and leak from their containers, forming a mixture inside the refrigerator/freezer.  Then, when ignited by a spark (i.e. the condenser unit coming on), they can explode.  Flammables should be stored in a flammable cabinet.


Some chemicals are capable of causing alterations in the DNA (genetic material).  Changes in the DNA can cause mutations, cancer and or reproductive damage.  These chemicals are referred to as “carcinogens” and are covered separately under the laboratory standard.  They must be kept in a secure and labeled area within the laboratory, and employees must handle them with extreme care, including personal protective equipment and proper ventilation. Current CAP regulations require all chemicals to be assessed for carcinogenicity, reproductive toxicity and acute hazards, as well.


There is no need to keep any mercury compounds in the histology laboratory.  There are many substitutes available today.  Do the substitutes work as good as the original mercury compounds?  Sometimes yes, sometimes no.  Do the substitutes work well enough for the pathologist to make a diagnosis?  Most certainly – yes.

You should dispose of your mercury thermometers and replace them with organic filled thermometers as well.  Mercury is a very toxic poison, and has no place in today’s histology laboratory.


    1. Theory and Practice of Histological Techniques. Chapter 10.  JD Bancroft, A Stevens ed.  Churchill Livingstone, NY.  Fourth edition. 1996
    2. Theory and Practice of Histotechnology.  Chapter 9.   DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
    3. CM Chapman.  Histology Study Group.  Presented at Region I meeting,     hosted by MaSH.  2014.