Wood preservation facilities, pentachlorophenol pressure: chapter E-4


4. Human Health Concerns

Human health effects from low PCP environmental concentration are unknown. Acute, high-dose exposure to PCP can induce a hypermetabolic state and excessive heat production. Effects--including hyperthermia, hypertension and metabolic acidosis--were observed in adults and children severely exposed to PCP through ingestion, inhalation or skin absorption. Death can result from seizures and cardiovascular collapse. In animals, chronically administered high doses of PCP were hepatotoxic and carcinogenic, and they adversely affected thyroid function. PCP is not mutagenic or teratogenic (17).

The International Agency on Research for Cancer has determined that PCP is classified in Group III, “possibly carcinogenic to humans” (18). PCP is absorbed rapidly via the lungs, gastrointestinal tract and skin (9). After absorption, PCP is distributed to most tissues and is not extensively metabolized (17).

After a single dose, PCP is eliminated over a few days; with repeated or chronic exposure, the elimination half-life may be a week or more. Most of the PCP taken into the body does not break down, but instead is eliminated via the urine. Much smaller amounts are eliminated in feces. Only a small amount is exhaled. Some of the PCP taken into the body is joined with other natural chemicals that render it less harmful. The combined product can then leave the body more easily (18). Finding a measurable amount of PCP in urine does not mean that the level of PCP causes an adverse health effect (17).

Considering previous studies on the effects of PCP effects and the limitations of these studies, it can reasonably be argued that exposure to PCP is associated with increased risks of a number of diseases, namely chloracne, soft tissue sarcoma, non-Hodgkin’s lymphoma and possibly abnormal births (10).

One safety objective of the industrial use of any chemical is to minimize worker exposure. If safeguards are not provided or are not implemented, a variety of human health effects can occur depending on the duration and manner of exposure, the concentration of the chemical to which exposure has occurred, the form of the chemical (e.g. ionic vs. non-ionic) and the varying metabolic sensitivities of individual workers.

The PMRA’s re-evaluation decision for the registration of the heavy duty wood preservatives creosote, pentachlorophenol, chromated copper arsenate and ammoniacal copper zinc arsenate, has granted continued registration of these products for sale and use in Canada. Potential risks from inhalation and dermal exposure were identified for some occupational tasks within wood-treatment facilities. The addition of new risk-reduction measures and the development of a Risk Management Plan for heavy duty wood preservatives will continue to lower the potential for occupational exposure for treatment facility workers (6).

Table 4, which is based on information from existing literature, outlines the spectrum of human health effects that could result from various degrees of exposure to PCP (as purified PCP).

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