Wood preservation facilities, chromated copper arsenate: chapter B-6


6. Protection of Personnel

Electronic copies of the pesticide labels for all registered Chromated Copper Arsenate (CCA) products, which contain information on product handling precautions, minimum worker protective equipment and health hazard warnings, can be obtained at the Health Canada (7). The conditions of use specified on the pesticide label are mandatory by law. Ensure that the information on the most current product label is followed.

6.1 First Aid, Precautions and Hygiene for CCA Exposure

The general rule for dealing with exposure is as follows: 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. If there is any doubt as to the concentration, the response should be the same as for the most concentrated form.

Facility staff should have access to pesticide 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 CCA solution, making the first aider the next victim if direct mouth-to-mouth contact is made.

Table 5 details the first aid measures for different type of exposure to CCA. First and second actions are described to provide hierarchic step by step actions.

For all medical attention, always take the pesticide label to show to the health personnel.

Personnel should follow the recommendations from Table 6 of Chapter A outlining general precautions and personal hygiene measures.

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 facility.

Specific limits for worker protection are generally prescribed by provincial regulations. Consult your local authorities for specific applicable regulations.

Most of the criteria are based on the TLVs and BEIs recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The ACGIH limits of exposure in the workplace are specified in Table 4.

Skin and Eye Contact

Chromated copper arsenate, as such, is not discussed by the ACGIH. With reference to skin and eye contact, the ACGIH provides the following conclusions in its support rationale (22) for TLV levels for individual components of CCA:

  • Copper salts act as irritants that may produce itchy eczema on skin and conjunctivitis or ulceration of the eye. However, the TLV for copper salts is based on inhalation.
  • Hexavalent chromium may cause contact dermatitis and skin ulcers, and may be absorbed through skin to cause kidney damage.

Nonetheless, ACGIH-recommended limits for copper, chromium and arsenic are based only on “inhalation” TLVs. These limits may not adequately take into account routes of exposure other than inhalation. The ACGIH has suggested that in such cases, “biological exposure indices may be useful as a guide to safe exposure” (22)

Inhalation

The ACGIH has defined TLVs for many substances based on exposure by inhalation and/or by skin exposure. The ACGIH limits for copper, chromium and arsenic are based solely on exposure by inhalation. The TLVs stipulated by the ACGIH are those “airborne concentrations of substances to which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effects.” The TLVs for copper, chromium and arsenic (22) are defined in Table 4 with the following provisos of the ACGIH:

  • “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 concentration.”
  • “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.”

Since CCA wood preservation facilities exclusively use CCA water solutions, the limits as defined by the ACGIH would apply primarily to suspended aerosols, dusts or gases generated during welding or at the cylinder door when pulling charges. Generally, airborne contaminant are not generated in CCA facilities at quantities that would cause worker health problems. Incidents of aerosol exposure would be more probable at improperly maintained facilities (i.e. from leaking seals) or at inadequately designed or maintained facilities (e.g. from vacuum pump discharges to the work area). Nevertheless, incidental exposure in well-designed and maintained facilities can occur and are of equal concern. Dust generation is most probable from forklifts and trucks moving on the drip pad and the yard and is also expected from cleaning operations. Frequent washdowns of pads and collection of the sump contents should minimize airborne contaminants caused by pad traffic. The International Labor Organization strongly suggests the use of wet or vacuum methods for cleaning up chromium solution spills, to prevent dispersion as airborne dust.

Ingestion

Oral intake of CCA must be avoided. Ingestion of CCA-containing liquids is unlikely if workers follow the precautions outlined in Table 8. Acceptable limits of ingestion are not prescribed by regulation, since it is generally expected that no such intake will occur. Reported fatal single dose levels for components of CCA, include

  • 0.7 g chromium as Cr+6 assuming a 70-kg body weight (13); and
  • 14 g copper as Cu+2 (23).

Oral toxicity values of arsenic As+5 to humans are not defined. Reported fatal doses for “arsenic” and “As+3” have ranged from 20 to 300 mg (13, 24). The Registry of Toxic Effects (20) suggests that As+5 is more acutely toxic to rats than As+3; however, it is known that laboratory animals react to arsenic differently than do humans. An absolute lethal dose to a person of As+5 as used in CCA, therefore, cannot be derived from animal data and remains unknown. However, because As+5 is partially metabolized into As+3, its potential toxicity should be assumed to be as high as that of As+3.

6.3 Safety Precautions

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

Table 8 describes additional safety precautions for personnel working specifically with CCA. User should refer also with Part I, Chapter A - Table 8 since both tables should be used in conjunction.

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.

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