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Control chemical exposures

Reducing worker’s exposure to chemicals is a fundamental concept in the protection of employee health. Even for chemicals for which an occupational exposure limit such as a Threshold Limit Value® exists, reducing exposures to the lowest feasible level is a common objective.

The accepted approach to this is to implement engineering controls, including ventilation and shielding, to apply administrative controls, such as leaving lab coats in the lab before exiting to a clean area, and to use personal protective equipment as appropriate. The efficacy of the first two is assessed by measuring actual exposures and the third is used to control exposures not controlled by the first two.

Laboratory workers usually do not think of controlling exposures. In general, laboratories are engineered to provide sufficient ventilation to control routine exposures. Most work which has the potential to create a breathing zone exposure hazard is performed in a fume hood. Here are some tips to think about to reduce exposures, even when working in a well-designed laboratory.
Minimize exposures with engineering controls and administrative techniques

Engineering controls operate with minimum intervention by laboratory personnel. Normal room ventilation, typically 6 – 10 complete changes of the room air per hour is sufficient to remove fugitive emissions from containers and experiments. Flow rates across the face of hoods can be controlled by lab personnel. While there is debate as to the optimum flow rate for efficient capture of gases, vapors or mists, most hoods are marked with an optimal sash level. Lab personnel must place the sash at this level as part of their work.

Some labs have engineered interlocks on equipment to prevent unsafe operations. Some labs have engineered static electricity controls or special electrical installations to prevent flammable vapor ignition. Lab personnel must be familiar with all of these engineering controls to insure that they function properly.
Install and maintain automatic monitors and alarms

Some labs handle large amounts of flammable or toxic liquids or gases. Some labs handle large amounts of Nitrogen, Argon, or similar asphyxiant gases. Some labs handle significant amounts of radioactive materials. Any location with these or other hazards need automatic monitoring systems to detect the presence of high levels of the hazardous substance and to alert personnel to the condition.

These systems require routine maintenance. Lab personnel must understand the operation of the sensors and have specific procedures to follow in the event of an alarm.
Develop a regular chemical monitoring program in work areas

Every laboratory should be periodically monitored to determine the level of exposure of personnel to the chemicals used in the area. The frequency and specific monitoring plan should be developed by trained specialists in conjunction with the laboratory director.
Provide routine medical monitoring of employees

Depending on the chemicals used in a laboratory, medical monitoring of personnel may be necessary. For example, a laboratory in which Carbon monoxide is used should provide periodic end-of-shift monitoring of potentially exposed personnel’s blood. The presence of carbonmonoxy hemoglobin in excess of 3.5% of total hemoglobin suggests that engineered control measures are not working. The American Conference of Governmental Industrial Hygienists (ACGIH) publishes a list of chemicals for which a Biological Exposure Index has been established.
Use protective shields and guards as needed

Some processes, particularly those operating well below or well above ambient pressure or temperature will require mechanical shielding to prevent personnel from harm in the event of a system failure. The need for such shielding shuld be evaluated as part of a routine laboratory safety review.
Use proper eye, face, hand, and body protection as needed

Most lab personnel accept the need for eye protection, gloves and lab coats. However, most lab personnel are not familiar with how to use this equipment properly. The selection of gloves is critical for preventing dermal exposures. Not all gloves protect equally against penetration by all chemicals. While light-weight Nitrile gloves are adequate for routine procedures, they are not adequate for chemicals such as Toluene, N-Methyl Pyrrolidone or Demethylformamide.

Safety glasses are the minimum level of eye protection in a laboratory. Splash goggles, full face shields or other special equipment must be used when needed.

Lab coats serve the purpose of keeping low levels of contamination off of personal clothing. Lab coasts belong in the lab, NOT in the cafeteria. Lab coats should be cleaned regularly.

All protective equipment should be used as part of a complete laboratory safety program.

Practice good personal hygiene around chemicals

Personnel should avoid behavior that promotes hand-to-mouth transfer of lab chemicals. Touching your face while wearing gloves, eating drinking or smoking in the lab and not washing your hands after removing gloves all raise the potential that low levels of contaminants on your hands will be ingested. Being aware of this helps control such behavior.
Discuss your chemical exposures with your healthcare provider

If you work around chemicals, be sure to discuss the interaction of any medications you may be taking and the chemicals used with your healthcare provider.
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Neal Langerman – On line 12/02/2008

Your comments: neal@chemical-safety.com

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