Methods For Controlling Chemical Exposures

Often, there are several alternative approaches to controlling hazardous exposures. Some are more reliable and effective than others. When selecting a control for your workplace, here is the preferred hierarchy from most to least effective.

Control At The Source

Substitution: Many chemicals and processes in use today are a long-standing matter of tradition. Although less harmful alternatives often exist, substitution can be a complex and expensive proposition that requires years of research and experimentation. If successful, however, it is the best approach since this has the potential to completely eliminate the hazard.

Isolate / Enclose The Process: Contain the chemical at the source by building a physical enclosure, separate room, or building. If this is not possible, try establishing a restricted area. Minimize the time and number of exposed persons to essential activities or off-shift employees.

Control Along The Path

Local Exhaust Ventilation: A mechanical exhaust hood near the point of chemical release can capture contaminated air before it spreads into the breathing zones of nearby employees. Contaminated air is drawn through ductwork to an air cleaner or exhausted to a safe area. This is an energy-efficient control because small volumes of air are needed and the contaminant is removed from the workplace.

General Ventilation: General ventilation requires the introduction of fresh air into the work environment to dilute the amount of airborne chemicals. This works but is not as desirable of an approach for several reasons: (1) levels of chemicals will still be high at the source; (2) if the system is not designed for good mixing of the room air, then there still may be pockets of high levels of chemicals; and (3) it can be expensive to operate because of the high energy requirements needed to move large volumes of air.

Housekeeping: Removal of chemicals from work surfaces (floors, walls, machinery, tools, etc.) is an effective control to minimize airborne dust levels. Wet-wiping, wet-mopping, and vacuuming are preferred over dry-wiping and sweeping since this will create less dust and result in cleaner surfaces. (Compressed air cleaning should be avoided.) Spills should be cleaned up as soon as possible.

Control At The Worker

Safe Job Procedures: Develop work practices and operating procedures that reduce the opportunity for exposure. Examples might include closing process and solvent containers when not in use, or performing welding in the presence of the provided ventilation system. These controls can be unreliable and difficult to implement since employees can choose to disregard them.

Worker Education: Train employees on the hazards of the chemicals they use, proper work procedures to minimize exposures, the rationale for these procedures, how to detect unsafe conditions, and how to respond to emergencies. It is a good idea to ask for worker ideas on how minimize hazards. They are more likely to support the ideas that they contribute.

Enclose The Worker: Locate employees inside of a control booth or room. This room needs to be comfortable and under a slight positive pressure to keep out contamination.

Personal Protective Equipment (PPE): Use of PPE (respirator, gloves, chemical protective clothing, etc.) is considered the last line of defense. Why? If PPE is not selected, used and fitted correctly, it does not provide protection and unsafe exposures continue. For this reason, PPE use should be limited to:

the time period necessary to install or repair engineering controls
maintenance and repair activities
situations where other controls are not sufficient
emergency situations

Plus, over the long run, the cost of a PPE program can be more expensive than some engineering controls. For example, use of respirators requires the ongoing administration of a written program, periodic replacement of equipment and cartridges, fit-testing, medical monitoring, training, etc.

Summary

All unsafe exposures need to be controlled. Fortunately, there are a wide variety of available options, some more reliable than others. In general, the higher the health risk, the higher the priority for action and the more reliable the control method needed. In reality, however, a variety of factors need to be considered when choosing the most effective control strategy. These may include:

Magnitude of the health risk
Technical feasibility of the control
Economic feasibility of the control
Reliability of the control method
Employee acceptance
Maintenance requirements
Consequences of control failure
Associated safety hazards
Associated environmental hazards

Resources

Certified Industrial Hygienists (CIH) are trained to provide guidance in choosing the best options for controlling exposures and can verify their effectiveness by reassessing the work environment after installation.