Respiratory protective equipment effectiveness

The immediately dangerous to life or health (IDLH) air concentration values have been recommended by the US National Institute for Occupational Safety and Health (NIOSH) as respirator selection criteria. The current NIOSH definition for an IDLH condition is a situation that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. NIOSH s stated purpose for establishing IDLH values is to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment. The complete introduction and documentations to the 398 existing IDLH values can be read or downloaded at the NIOSH Internet website. 

The fact that these concentrations have been measured does not mean that occupational exposures occur persons may use respiratory protection equipped to prevent exposure. All persons who have excessive occupational exposure to isocyanates may experience primary irritant effects in the respiratory tract depending on the extent of excessive exposure. Brief accidental exposures to concentrations of isocyanates tenfold or more above the TLV may cause short term respiratory irritation with recovery 24-48 hours following cessation of exposure. Continuing repeated workday exposures several-fold higher than the TLV can cause chronic respiratory irritation. All individuals will not suffer the same degree of respiratory irritation from excessive exposures due to individual biochemical and physiological differences. Studies have shown that on the order of five percent of persons who have had an occupational exposure to TDI develop a bronchial asthmatic type of response to subsequent exposures that are below concentrations causing any detectable primary irritation. 

Lead dust or fiime in the workplace atmosphere should, in so far as possible, be controlled to levels within the legal limits by means of effective exhaust ventilation coupled with suitable arrestment facilities. In situations where exposure cannot be adequately controlled by these means, the use of respiratory protective equipment on the part of the workers becomes necessary. Indeed as blood lead limits become lower, the wearing of respirators has become routine in many plants, not just to protect the worker from airborne lead but because it has the added advantage of preventing hand-mouth contact and consequent ingestion of lead. 

Personal protective equipment. Personal protective equipment designed to protect against exposure by inhalation is known as respiratory protective equipment (or RPE). Such equipment should not be used as a long-term method of ensuring that exposures are reduced to acceptable levels. This is because it is prone to mechanical failure and human error. RPE may be used appropriately for specific short-term operations (e.g. some maintenance tasks) where it is not practicable to reduce exposures to acceptable levels by other means. It may also be of value in emergency situations. Positive pressure breathing apparatus (line fed or self-contained) is preferable to canister-type respirators. For RPE to be effective when required, it must be adequately maintained and personnel fully trained in its use. 

Immunologic Sensitivity to beryllium was investigated among 362 workers at an aluminium smelter in Norway [40 ]. One had abnormal results in two separate blood samples and was sensitized to beryllium. Three others had one abnormal test that was not confirmed by a second test. One of a control group of 31 people had one abnormal and one normal test result. This frequency of beryllium sensitivity is much lower than is found in the beryllium handling industry, which the authors attributed to lower atmospheric concentrations, beryllium speciation effects, or the use of respiratory protective equipment. 

A complete and detailed work history is important in the initial evaluation. A listing of all previous employment with information on job description, exposure to fumes or dust, known exposures to lead or other toxic substances, a description of any personal protective equipment used, and previous medical surveillance should all be included in the worker s record. Where exposure to lead is suspected, information concerning on-the-job personal hygiene, smoking or eating habits in work areas, laundry procedures, and use of any protective clothing or respiratory protection equipment should be noted. A complete work history is essential in the medical evaluation of a worker with suspected lead toxicity, especially when long term effects such as neurotoxicity and nephrotoxicity are considered. 

For occupational risk characterisation, this should be conducted, in the first instance, without the incorporation of Personal Protective Equipment (PPE) or Respiratory Protective Equipment (RPE). If required, the protective effects of PPE and/or RPE can be used to refine the risk characterisation for appropriate exposure scenarios. If the use of PPE and/or RPE is necessary to reduce the risk to an acceptable level then this would form part of the decision-making process and the appropriate PPE and RPE would have to be included onto the product label. 

The purpose of establishing an IDLH exposure concentration is to ensure that the worker can escape without injuty or irreversible health effects from an IDLH concentration in the event of failure of the respiratory protective equipment. The IDLH is considered a maximum concentration above which only highly reliable breathing apparatus providing maximum worker protection is permitted. As IDLH values are set conservatively, any approved respirator may be used up to its maximum use concentration below the IDLH. 

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