Wood preservation facilities, ammoniacal copper zinc arsenate: chapter C-6

6. Protection of Personnel

6.1 First Aid, Precautions and Hygiene for ACZA Exposure

Human health effects could occur as a result of improper controls during manual preparation of ACZA, exposure to minor spills and residues in working areas, and improper handling of treated products. When exposure to a chemical occurs, the severity and speed of damage to human health depends on the concentration. The general rule 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. Immediate response is required if a worker is exposed to aqua ammonia, arsenic acid or ACZA concentrate or work solutions. Table 5 outlines first aid measures for exposure to ACZA and its constituents.

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 ACZA solution, making the first aider the next victim if direct mouth-to-mouth contact is made.

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

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 Tables 4.0 to 4.1 above.

Skin and Eye Contact

For skin and eye contact with individual components of ACZA, the ACGIH provides the following comments (11):

• A TLV of 25 ppm ammonia has been selected to protect against irritation to eyes and the respiratory tract and to minimize discomfort among unaccustomed workers.
• Copper salts act as irritants and can produce itchy eczema on skin, and conjunctivitis or ulceration on the eye. However, the TLV for copper salts is based on inhalation.
• Adequate skin and eye protection is required during the handling of all acids, including arsenic acid. ACGIH-recommended limits for arsenic acid are based on the “inhalation” TLV.

In cases where ACGIH-recommended limits (e.g. for copper and arsenic) are based only on “inhalation” as the route of exposure, these limits may not adequately take into account other routes of exposure. The ACGIH has suggested that in such cases, “biological exposure indices may be useful as a guide to safe exposure” (11).

Inhalation

The ACGIH has defined TLVs for many substances based on exposure by inhalation and/or by skin exposure. The ACGIH limits for copper and arsenic are based solely on exposure by inhalation. The TLVs are stipulated by the ACGIH as 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 short-term limit is defined as “a 15-minute TWA [time-weighted average] exposure, which should not be exceeded at any time during the work day.” The TLVs for ammonia, copper, zinc and arsenic (11) are defined in Table 4.0 to 4.1 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.”

Ingestion

Oral intake of ACZA must be avoided. Ingestion of ACZA-containing liquids is unlikely if workers follow the safety precautions outlined in Table 8. Upper limits of ingestion are not prescribed by regulation, since it is generally expected that no such intake will occur.

Oral toxicity values of As+5, to humans are not defined. Reported fatal doses for “arsenic” and “As+3” have ranged from 20 to 300 mg (11, 13). Reported fatal single dose levels for components of ACZA, include 30 mL of 25% ammonia solution (11); and 1.5 to 3.5 g of Cu as Cu+1 (11).

The Registry of Toxic Effects suggests that As+5 is more toxic to rats than As+3; however, it is known that laboratory animals react differently to arsenic than do humans. The lethal toxicity to humans of As+5 as used in ACZA, 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 safety precautions outlined in Table 8. in addition to those recommended 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.