As previously indicated, exposure to toxic chemicals can seriously affect health. However, if appropriate precautions are taken, these chemicals can be handled safely. There are a variety of methods which provide protection from such exposures. The design of the workplace, the work practices and hygiene
practices followed, and the protective equipment worn may all be essential in controlling exposure to toxic substances. The protective measures which must be considered include:
Ideally, the toxic substance used or generated should be eliminated. Since this is not always possible, substituting a less hazardous substance can often be effective in reducing work exposure to toxic substances.
eg. If it necessary to use benzene for cleaning; usually, 1,1,1-trichloroethane will do the job just as well.
Hazardous processes or equipment can be segregated into separate rooms or areas or put in enclosures so as not to contaminate the whole workplace.
eg. Operator booths are common in crusher operations (extremely dusty environments), crane cabs in hazardous areas, etc.
b. Design or Change of Process
Often simple considerations can significantly improve conditions.
eg. packaging of exact amounts of material to add to a process rather than pouring, pumping, scooping, etc. from a bulk supply
eg. grouping of hazardous operations for better control.
c. Local Suppression
Wetting or pelletizing of dusty materials or blanketing of toxic liquids.
eg. Use of damp mopping in contaminated, dusty areas.
eg. Use of plastic balls or surface active agents in liquid tanks such as plating tanks.
Ventilation is used to control airborne hazards in the form of dusts, fibres, mists, fumes, gases, and vapours. The two methods of applying ventilation to provide contaminant control are: general dilution ventilation and local exhaust.
Dilution Ventilation – dilution of contaminated air with uncontaminated air in a general area, room, or building for the purpose of health hazard, nuisance control, and/or heating and cooling.
Local exhaust – involves the capture of pollutants at the source.
Air movement is achieved by either natural or mechanical methods (e.g. fans), and the choice or type of ventilation depends on such factors as:
- Toxicity or nuisance of the contaminant
- Method and rate of generation
- Physical state of the contaminant
- Relative costs of different types of ventilation.
Work Practices and Hygiene Practices
Work practices, procedures and hygiene practices supplement engineering controls. These practices represent on the job activities that reduce the potential for exposure to toxic substances and include:
- Posting warning signs and labelling hazardous materials
- Preventive maintenance of equipment.
- Keeping records of employee exposure and making them available to employees
- Providing emergency facilities, such as eyewash fountains and deluge showers, where appropriate
- Prohibiting eating, drinking or smoking in areas where materials in use are toxic by ingestion or may be inhaled through smoking.
- Maintaining good housekeeping – good housekeeping provides for the removal of hazardous materials that might otherwise become airborne. In addition, a clean workplace tends to foster good work habits that have a higher probability of reducing accumulations.
- Maintaining personal Cleanliness – clean work clothes, regular showers and frequent washing will reduce skin contamination that may lead to skin absorption, dermatitis or ingestion. A further consideration for personnel cleanliness is the possibility of an individual carrying toxic material home on work clothes or on the person and in turn placing the family at risk.
- Training – Individuals should be well aware of the hazards of the materials being used and the precautions to be observed. An informed worker can make a rational decision to accept such work and to wisely use the equipment provided for his protection.
Personal Protective Devices
These include protective glasses and goggles, face shields, protective clothing (laboratory coats and gloves), skin creams, and respirators. It should be noted that respirators in particular, are not intended to be used as a primary means of control in lieu of other methods.
Two essential elements of protective equipment use are:
- The choice of the proper type of protective equipment.
For example, when choosing respirators and hearing protectors, the factors to be considered include:
- type of hazard
- extent of exposure
- individual preference
- individual fit
- ease of supervision
- legislative requirements
2. The provision of an adequate maintenance program for the equipment.
A maintenance program for the equipment must be in the care of a qualified person and will include, at regular intervals:
a) Inspection and Repair – All parts should be checked to be certain that materials have not deteriorated, valves are working, etc. As necessary, equipment must be replaced or repaired. With respirators, new filters or cartridges must be made available to workers at all times. With self-contained breathing apparatus cylinders must recharged and all mechanisms checked.
b) Cleaning – Equipment must be cleaned, sterilized and dried after each use. While it is preferable for workers to have their own personal equipment, because of cost and other considerations, particularly with self-contained air supplied units, sharing may be necessary. In such cases cleaning and sterilizing becomes very important.
c) Storage – Equipment should be stored in clean, dry locations protected against extremes of temperature, humidity and sunlight.
Other Safe Practices and Emergency Provisions
a) Leak and Chemical Spill Procedure
Prompt action is necessary to reduce and eliminate hazards created by a chemical spill.
- Wear proper personal protective equipment (e.g. gloves, respirators) as specified in the SDS.
- Absorb or neutralize liquids.
- Sweep solids into a container.
- Ventilate area to dispel vapours if required.
- Wash affected area with soap and water or detergent.
- All materials used in clean-up, including absorbed liquids are to be disposed as hazardous waste. Label waste appropriately.
If proper equipment is not available to safely contain and decontaminate a spill – evacuate the area and contact the appropriate personnel.
Section 4.3 of the University of Toronto Health and Safety Policy Manual details chemical spill procedures. Also, consult the pertinent SDS.
b) Waste Disposal
The disposal of hazardous chemicals is regulated by Ontario environmental legislation. Generators of hazardous wastes are responsible for properly packaging and labelling such wastes. Section 4.2 of the University of Toronto Health and Safety Policy Manual details chemical waste disposal procedures. Also, consult the pertinent SDS.
c) Storage Requirements
The hazard potential presented by flammable, reactive and toxic substances can also be reduced by adherence to safe storage procedures.
- Quantities of these substances should be kept to a minimum.
- All containers must be labelled with the names of the contents and appropriate hazard warnings
- In laboratories or stockrooms, care should be taken to avoid exposure of chemicals to heat or direct sunlight.
- Always observe precautions regarding the proximity of incompatible substances (e.g. do not store alphabetically – store in compatible groups).
- Highly toxic chemicals should be stored in ventilated storage areas in unbreakable, chemically resistant secondary containers.
- Properly labelled portable safety cans should be used for handling small quantities of flammable liquids. When not in use, these portable cans should be kept in enclosed fire-resistant cabinets. Larger quantities of solvents should be stored in correctly designed ventilated stores.
- Flammable liquids should not be stored in laboratory refrigerators unless the unit is an approved, explosion-proof, or laboratory-safe type.