Sister chromatid exchange and chromosomal breakage in pentachlorophenol (PCP) exposed workers

Pentachlorophenol-induced cytotoxicity in human erythrocytes: enhanced generation of ROS and RNS, lowered antioxidant power, inhibition of glucose metabolism, and morphological changes

Pentachlorophenol (PCP) is a class 2B human carcinogen that is used as an insecticide, herbicide, and wood preservative. PCP is rapidly absorbed and enters the blood where it can interact with erythrocytes. We have examined the effect of PCP on human erythrocytes. Treatment of erythrocytes with PCP increased the intracellular generation of reactive oxygen and nitrogen species. It also increased lipid and protein oxidation accompanied by decrease in glutathione levels and total sulfhydryl content. The activities of all major antioxidant enzymes were altered. The antioxidant power was significantly impaired resulting in lower free radical quenching and metal reducing ability of the PCP-treated cells. PCP exposure also inhibited the activities of enzymes of glycolysis and pentose phosphate shunt, the two pathways of glucose metabolism in erythrocytes. Heme degradation was enhanced leading to the release of free iron. Incubation of erythrocytes with PCP caused significant cell lysis suggesting plasma membrane damage which was also evident from inhibition of bound enzymes. Scanning electron microscopy of erythrocytes confirmed these biochemical results and showed that PCP treatment converted the normal biconcave discoids to echinocytes and other irregularly shaped cells. Thus, PCP induces oxidative and nitrosative stress in erythrocytes, alters the enzymatic and nonenzymatic antioxidant defense systems, inhibits glucose metabolism, and causes significant modifications in cellular morphology.

Photocatalytic degradation of pentachlorophenol by N–F–TiO2: identification of intermediates, mechanism involved, genotoxicity and ecotoxicity evaluation

Heterogeneous photocatalysis using N–F codoped TiO₂ was successfully applied for degradation, mineralization as well as for genotoxicity and ecotoxicity elimination of PCP in the aqueous phase.

Pentachlorophenol Poisoning

Despite being banned in many countries and having its use severely restricted in others, pentachlorophenol (PCP) remains an important pesticide from a toxicological perspective. It is a stable and persistent compound. In humans it is readily absorbed by ingestion and inhalation but is less well absorbed dermally. Its distribution is limited, its metabolism extensive and it is eliminated only slowly. Assessment of the toxicity of PCP is confounded by the presence of contaminants known to cause effects identical to those attributed to PCP. However, severe exposure by any route may result in an acute and occasionally fatal illness that bears all the hallmarks of being mediated by uncoupling of oxidative phosphorylation. Tachycardia, tachypnoea, sweating, altered consciousness, hyperthermia, convulsions and early onset of marked rigor (if death occurs) are the most notable features. Pulmonary oedema, intravascular haemolysis, pancreatitis, jaundice and acute renal failure have been reported. There is no antidote and no adequate data to support the use of repeat-dose oral cholestyramine, forced diuresis or urine alkalinisation as effective methods of enhancing PCP elimination in poisoned humans. Supportive care and vigorous management of hyperthermia should produce a satisfactory outcome. Chronic occupational exposure to PCP may produce a syndrome similar to acute systemic poisoning, together with conjunctivitis and irritation of the upper respiratory and oral mucosae. Long-term exposure has also been reported to result in chronic fatigue or neuropsychiatric features in combination with skin infections (including chloracne), chronic respiratory symptoms, neuralgic pains in the legs, and impaired fertility and hypothyroidism secondary to endocrine disruption. PCP is a weak mutagen but the available data for humans are insufficient to classify it more strongly than as a probable carcinogen.

Association of elevated blood levels of pentachlorophenol (PCP) with cellular and humoral immunodeficiencies

It has long been suspected that pentachlorophenol (PCP) exerts a damaging influence on the immune system. In this study, the possible relationship between blood levels of PCP and immune function was studied in 190 patients who had been exposed for more than 6 mo to PCP-containing pesticides. The patients suffered from frequent respiratory infections and general fatigue. Lymphocyte subpopulations, in-vitro responses to mitogens, allogeneic stimulator cells, plasma neopterin, cytokines, soluble cytokine receptors, soluble adhesion molecules, and immunoglobulin autoantibodies were determined. A dose-response relationship between blood levels of PCP and cellular and humoral immune parameters was established. Blood levels of PCP were associated negatively with (a) total lymphocyte counts (p = .0002), CD4/CD8 ratios (p = .0015), and absolute counts of CD3+ (p < .0001), CD4+ (p < .0001), CD16+ (p < .0001), CD25+ (p = .0003), DR+ (p < .0001), CD8+/56+ (p = .020), and CD19+ cells (p = .092); (b) plasma levels of interleukin-2 (IL-2) (p < .0001), soluble IL-2R (p < .0001), IL-6 (p < .0001), IL-10 (p = .0039), interferon-gamma (IFN-gamma) (p < .0001), tumor necrosis factor-alpha (TNF-alpha) (p < .0001), transforming-growth factor-beta2 (p = .023), soluble IL-1 receptor antagonist (sIL-1 RA) (p < .0001), soluble intercellular adhesion molecule-1 (p = .0003); and (c) immunoglobulin (Ig) M-anti-Fab type autoantibodies (p = .0353). PCP levels were associated positively with (a) number of impaired stimulation assays per patient (p = .041); (b) number of circulating CD11b+ monocytes (p = .0015); and (c) plasma levels of neopterin (p < .0001), IL-4 (p = .020), and sIL-6R (p = .020). Compared with patients who had PCP plasma levels that were less than or equal to 10 microg/l, patients with blood levels of PCP that exceeded 10 microg/l experienced the following more often: low numbers of total blood lymphocytes (p = .054), CD3+ (p = .0014), CD4+ (p = .0001), DR+ (p = .0003), CD16+ (p = .0033), and CD25+ cells (p = .0033). In addition, the same aforementioned patients experienced the following more frequently: undetectable plasma levels of IL-2 (p = .0057), IL-6 (p = .042), IL-8 (p = .038), IL-10 (p = .0001), TNF-alpha (p = .0062), and IFN-gamma (p = .016); and impaired in-vitro responses of lymphocytes (p = .071). The authors concluded that increased blood levels of PCP were associated significantly with cellular and humoral immunodeficiencies. Recurrent respiratory infections and general fatigue could originate from PCP-associated immunosuppression.

Impaired in-vitro lymphocyte responses in patients with elevated pentachlorophenol (PCP) blood levels

Immune parameters were examined in 188 patients who were exposed for more than 6 mo to pentachlorophenol-containing pesticides. Blood levels of pentachlorophenol, lymphocyte subpopulations, in-vitro responses to mitogenic and allogeneic stimulation, plasma neopterin levels, and plasma cytokine and cytokine receptor levels were determined. Impaired in-vitro lymphocyte stimulation responses were impaired in 65% of the patients. The likelihood of impaired lymphocyte stimulation increased significantly with levels of pentachlorophenol that exceeded 10 microliters/l (p < .05). Patients who had high blood levels of pentachlorophenol and abnormal lymphocyte stimulation also had increased proportions of blood monocytes in blood (p < .05), as well as increased IL-8 serum levels (p < .02). Eleven patients who had abnormal mitogen stimulation experienced decreased CD4/CD8 ratios of < 1.0; 5 of these patients had decreased CD4+ lymphocyte counts of < 500/microliters, and 3 patients had increased plasma neopterin of > 15 nmol/l. These results indicate that increased levels of pentachlorophenol in blood can lead to severe T lymphocyte dysfunction.

Human pentachlorophenol poisoning

Pentachlorophenol (PCP) was, and still is, one of the most frequently used fungicides and pesticides. Its toxicity is due to interference with oxidative phosphorylation. Acute and chronic poisoning may occur by dermal absorption, inhalation or ingestion. Chronic poisoning occurs mainly in sawmill workers or people living in log homes treated with PCP-containing wood protecting formulations. Quantitative determination of PCP in urine and serum is useful to detect occupational or subclinical exposure. The clinical features of acute and chronic PCP poisoning can be classified systematically into effects on the skin, metabolism (fever), the haematopoietic tissue, the respiratory system, the central and peripheral nervous system, the kidney and the gastrointestinal tract. Although PCP is not classified as a human carcinogen, some epidemiological observations suggest that exposure to chlorophenols in general and PCP solutions in particular may result in an increased risk for certain malignant disorders such as nasal carcinoma and soft tissue sarcoma. There is concern that contamination of PCP-solutions with products such as chlorodibenzo-p-dioxins is the real cause of this suspected carcinogenicity. No specific antidote exists for the treatment of (acute) PCP poisoning. The basis of the treatment of acute poisoning is intensive supportive care with prevention of dangerous rise in temperature. Use of PCP-based products as indoor wood preservatives poses an unacceptable risk to human health.

Human lymphocyte reactivity after in vitro exposure to technical and analytical grade pentachlorophenol

To investigate the potential effects of technical pentachlorophenol (PCP-T, contaminated with polychlorinated dioxins and furans) and of analytical grade pentachlorophenol (PCP-A) on the human immune system, in vitro assays with freshly prepared human peripheral blood lymphocytes were used as an alternative to experimental animals. Both cell-mediated and humoral immune functions were examined after direct lymphocyte exposure to PCP-T or PCP-A at concentrations ranging from 0-200 microM. In each case the viability of the treated cells remained within the control value range. T lymphocyte blastogenesis after 3 days incubation with PCP was measured using both optimal and suboptimal mitogen (PHA) concentration. Interleukin-2 activity of 24.5-h supernatants of lymphocytes in response to PHA, pretreated with PCP for 20-24 h, was examined in a bioassay using the mouse IL-2-dependent CTLL-6 cell line. The synthesis of immunoglobulins was determined after stimulation with T-dependent (PWM) and T-independent (KlebsM) polyclonal B cell activators. In the proliferation assay the effects of PCP-T became more evident after suboptimal mitogen stimulation. Whereas after optimal mitogen stimulation blastogenesis was affected only at the highest concentration of 200 microM PCP-T, cell reactivity after suboptimal PHA stimulation was altered by all PCP-T doses. In the lower concentration range PCP-T caused enhanced proliferative responses, but at the two highest PCP-T concentrations cell reactivity was significantly suppressed as compared to the medium controls. Significant differences between the effects of PCP-T and PCP-A could be demonstrated only after optimal mitogen stimulation at the highest PCP concentration (200 microM). In contrast, lymphokine production as well as Ig secretion showed severe dose-dependent suppression after exposure to both PCP-T and PCP-A. The humoral immune response appeared to be more suppressed when cultures were stimulated with T-dependent rather than T-independent mitogens. The two different PCP preparations caused immunosuppression of both lymphocyte functions to the same extent. To summarize, the results of our studies indicate that PCP itself is directly immunotoxic to human immunocompetent cells and the T helper cell subset appears to be especially sensitive to PCP exposure. Furthermore, the observation of a direct effect on humoral immunity is similar to previous results showing considerable alterations of antigen specific antibody production in experimental animals after in vivo exposure.

Pentachlorophenol

Pentachlorophenol (PCP) is a substance whose widespread use, mainly in wood protection and pulp and paper mills, has led to a substantial environmental contamination. This in turn accounts for a significant exposure of the general human population, with rather high exposure levels being attained in occupational settings. Investigations on the genotoxic activity of PCP have given rise to divergent results which would seem to make an evaluation difficult. By grouping them into 3 categories a somewhat clearer picture, allowing finally an (admittedly tentative) assessment, can be obtained. PCP does seem to be at most a weak inducer of DNA damage: it produces neither DNA-strand breaks nor clear differential toxicity to bacteria in rec-assays in the absence of metabolic activation. Also in SCE induction no increase can be observed in vivo, while PCP is found marginally active in a single in vitro experiment. Metabolic activation, however, leads to prophage induction and to DNA strand breaks in human lymphocytes, presumably through the formation of oxygen radicals. A possible further exception in this area might be the positive results in the yeast recombination tests, although their inadequate reporting makes a full evaluation difficult. PCP does not seem to induce gene (point) mutations, as most bacterial assays, the Drosophila sex-linked recessive lethal test and in vitro assays with mammalian cells did not demonstrate any effects. Marginally positive results were obtained in the mammalian spot test in vivo and in one bacterial test; the positive result in the yeast assay for cycloheximide resistance is fraught somewhat with its questionable genetic basis. PCP does, however, induce chromosomal aberrations in mammalian cells in vitro and in lymphocytes of exposed persons in vivo. Those in vivo results that were unable to provide evidence of chromosomal damage are hampered either by methodological inadequacies or by too low exposure levels. The (rodent) metabolite tetrachlorohydroquinone might be a real genotoxic agent, capable of binding to DNA and producing DNA strand breaks; this activity is probably due to semiquinone radical formation and partly mediated through active oxygen species. Since this compound has not been tested in the common bacterial and mammalian mutagenicity assays, the few ancillary results on this substance cannot be used in a meaningful human risk assessment of PCP. Furthermore, this metabolite has only been produced by human liver microsomes in vitro, but has not been detected in exposed humans in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)