Wood preservation facilities, pentachlorophenol pressure: chapter E-6

6. Protection of Personnel

With the use of PCP, it is important to provide protection against all potential types of exposure: eye contact, skin contact and inhalation. Many work situations require protection against more than one type of exposure--for example, when chlorophenol dusts, aerosols or vapours are produced. In these situations, the use of nose-mouth respirators that do not cover the eyes or the skin around the eyes may lead to a false sense of security. PCP is absorbed rapidly via the skin (13). Full face shields or full-face cartridge respirators should be used.

6.1 First Aid, Precautions and Hygiene for PCP Exposure

Table 5 contains the recommended actions in case of PCP exposure. The higher the concentration of a preservative to which a worker is exposed, the greater the need for protective measures and immediate response if contact occurs.

Facility staff should have access to product labels and appropriate training to apply first aid.

First aid personnel should periodically verify up-to-date response measures with chemical suppliers and/or industrial physicians.

Artificial respiration should not be performed without the use of a barrier device, as the injured person may be contaminated (on skin) with PCP solution, making the first aider the next victim if direct mouth-to-mouth contact is made.

For all medical attention, always have the Pest Control Products label and the MSDS at your disposal so that you can properly inform health personnel.

6.2 Regulatory Controls

The labels for pesticide products contain information on the minimum necessary protective equipment and practices for using the product. The worker protection measures on the pesticide label are mandatory. Provincial or municipal regulations may require additional measures that may enhance, but not reduce, protection. Table 7 in Chapter A can be used to summarize the local regulatory threshold limit values (TLVs) and/or biological exposure indices (BEIs) applicable to the plant.

Most regulatory criteria established by worker protection agencies are based on TLVs and BEIs, as recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) (25). The ACGIH threshold limit value-time weighted averages (TLV-TWAs) for chemicals are defined with the following provisos:

• “The limits are intended for use in the practice of industrial hygiene as guidelines for good practices or recommendations in the control of potential health hazards and for no other use” (i.e. proof or disproof of the cause of an existing disease or physical condition).
• “The limits are not fine lines between safe and dangerous concentrations.”
• “In spite of the fact that serious injury is not believed likely as a result of exposure to the Threshold Limit concentrations, the best practice is to maintain concentrations of all atmospheric contaminants as low as is practical.”
• “When two or more hazardous substances, which act upon the same organ system, are present, their combined effect, rather than that of either individually, should be given primary consideration.”

Recently, the ACGIH has suggested augmenting TLV workplace evaluations by using “biological exposure indices (BEI) which may be useful as a guide to safe exposure” (25). See section 6.4 for more details.

Skin and Eye Contact

The ACGIH-recommended TLV-TWA for PCP represents a time-weighted average (TWA) concentration “for a normal 8-hour workday and a 40-hour work week, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.” The recommended TLV-TWA value for PCP is 0.5 mg/m³, and is followed by the designation “skin,” which refers to “the potential contribution to the overall exposure by the cutaneous route including mucous membranes and eyes, either by airborne, or more particularly, by direct contact with the substance” (25).

In practice, a wide range of dermal exposure to PCP can be encountered in the wood treatment workplace (i.e. from pure PCP solids to waters containing a few parts per million PCP). Dermal penetration is a significant route of PCP intake, and this penetration is enhanced if exposure to PCP/oil solution occurs (26).

Inhalation

The ACGIHTLV-TWA considered that the PCP values for skin and eye contact would also be applicable to the maximum allowable values for inhalation. In its rationale for using TLV-TWAs, the ACGIH makes the following statement about PCP: “Dusts are particularly irritating to the eyes and nose in concentrations greater than 1 mg/m³. Some irritation may occur at 0.3 mg/m³. Seasoned workers can tolerate up to 2.4 mg/m³” (25)

A review of the literature indicates that many of the documented industrial health incidents involving PCP have occurred as a result of dumping bagged PCP flakes (formerly used) in poorly ventilated areas (26, 27, 28). Other exposures to dusts may occur during activities such as cleanup of spilled PCP solids. Facility operators must ensure that adequate designs and operational procedures are in place in order to minimize worker exposure to PCP dusts (i.e. adequate local ventilation, use of appropriate respiratory equipment, and use of wet or vacuum methods for cleaning of spilled PCP solids). Other potential sources of inhaled PCP include vapours in the vicinity of charge removal areas and in the vicinity of freshly treated wood, and aerosols at improperly maintained facilities (e.g. from leaking seals) or at inadequately designed facilities (e.g. from vacuum pump discharges to work areas).

Ingestion

Oral intake of PCP must be avoided. Ingestion of PCP or liquids that contain PCP is unlikely if workers follow elementary rules of good hygiene. Acceptable limits of ingestion are not prescribed by regulation, since there is no valid reason for any such intake to occur. The single dose level of PCP known to result in fatality is in the order of 1 to 3 g (29, 30).

6.3 Safety Precautions

All facility workers who have any potential for dermal exposure to PCP, oil solutions of PCP, or freshly treated wood should be required to adhere to minimum levels of protection and hygiene. The level of protection should increase with increasing potential for exposure to PCP.

Workers need to familiarize themselves with the safety precautions presented in Table 8 in addition to those mentioned in Chapter A, Section 6.3. Sensitive individuals should take special care to avoid exposure.

6.4 Biological Monitoring of Exposed Workers

Biological monitoring is a useful tool for evaluating the long-term effectiveness of the protective measures applied. Routine biological monitoring of exposed workers (primarily those who handle preservatives and treated wood, e.g., plant operators and quality control personnel) is recommended. Refer to Chapter A, Section 6.4

Blood PCP exposures are good indicators of acute short-term exposures because blood PCP values reach maximum 4 hours after exposure. It is useful for monitoring PCP exposures via skin contact, inhalation and ingestion. The BEI in blood is measured in plasma, at the end of shift, prior to the last shift of the workweek, and is set at 5 mg/L. Chronic exposures can best be monitored by measuring PCP in urine. BEI for total PCP in urine = 2 mg/g creatinine sampled prior to last shift of workweek at the end of shift (25).