Occupational exposure to phenoxy herbicides and chlorophenols and cancer mortality in The Netherlands

As part of the "IARC International Register of Persons Exposed to Phenoxy Herbicides and Contaminants," a cohort of workers who manufacture and prepare chlorophenoxy herbicides was recruited in The Netherlands. The cohort comprised 2,310 workers from two plants, operated by different companies, who were followed during the periods 1955-1985 and 1965-1986, respectively. In 1963, there had been an industrial accident in one factory with concomitant release of dioxin into the environment. Loss to follow-up was 3%. Mortality data on 963 exposed and 1,111 nonexposed men were evaluated by external and internal comparison. Compared with national rates, total mortality (94 deaths, standardized mortality ratio [SMR] = 101; 95% confidence interval [CI], 82-124) and cancer mortality (31 deaths, SMR = 107; 95% CI, 73-152) for exposed workers were not significantly increased. A statistically insignificant increase was observed for non-Hodgkin's lymphoma (2 deaths, SMR = 299; 95% CI, 36-1,078). No cases of soft-tissue sarcoma were encountered. There was no increase in either total mortality (25 deaths, SMR = 111; 95% CI, 72-163) or cancer mortality (10 deaths, SMR = 137; 95% CI, 66-252) among the 139 workers probably exposed to dioxins during the 2,4,5-trichlorophenol production accident or the subsequent clean-up operations. Compared with nonexposed workers, exposed workers did not exhibit a higher total mortality (rate ratio [RR] = 1.28; 95% CI, 0.89-1.82). Mortality due to all cancers (RR = 1.7; 95% CI, 0.9-3.4) and respiratory cancer (RR = 1.7; 95% CI, 0.5-6.3) was insignificantly elevated. These findings suggest that the increases in cancer mortality among workers exposed to phenoxy herbicides and chlorophenols may be attributable to chance. Lack of power prevented evaluation with respect to specific cancers.

Internal exposure to organic substances in a municipal waste incinerator

Fifty-three persons occupied in a municipal waste incinerator were examined with respect to their internal exposure to organic substances which may be produced during pyrolysis of organic matter. For this purpose the levels of benzene in blood, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in plasma, and mono- (MCPs), di- (DCPs), tri- (TCPs), tetra- (TCEPs) and pentachlorophenol (PCP) and hydroxypyrene in urine were determined. For control purposes, 431 men and women were examined. Significantly higher values for the workers were found for the excretion of hydroxypyrene [median (m): 0.24 vs 0.11 microgram/l; non-smokers], 2,4/2,5-DCP (m: 10.5 vs 3.9 micrograms/l) and 2,4,5-TCP (m: 1.2 vs 0.8 micrograms/l) and for the HCB level in plasma (m: 4.4 vs 2.8 micrograms/l). For the concentrations of 4-MCP and 2,3,4,6/2,3,5,6-TECP, the controls had significantly higher concentrations in urine than did the workers in the incineration plant (m: 4-MCP 1.7 vs 1.2; 2,3,4,6/2,3,5,6-TECP: 1.2 vs 0.3 micrograms/l). No significant differences between workers and controls were detected with respect to benzene in blood (m: 0.20 vs 0.28 microgram/l; non-smokers), 2,4,6-TCP and PCPs in urine (m: 0.85 vs 0.60 and 2.2 vs 2.2 micrograms/l) or the levels of PCB congeners in plasma (m: sigma 138, 153, 180: 5.6 vs 4.1 micrograms/l). The elevated levels of hydroxypyrene, 2,4/2,5-DCP, 2,4,5-TCP and HCB in biological material may be related to the incineration of the waste. These elevations, however, are very small and are of interest more from the environmental than from the occupational point of view.

Phenoxy herbicides and chlorophenols: a case control study on soft tissue sarcoma and malignant lymphoma

A case control study on patients with soft tissue sarcoma and malignant lymphoma was undertaken to test whether there was any association between these diseases and past exposure to chlorinated phenoxy acid herbicides or chlorophenols. It was carried out over the period 1982-1988 in Victoria, Australia. Thirty males with soft tissue sarcoma and 52 males with malignant lymphoma were matched by age, place of residence and sex with one population control and one cancer control each. Exposure was assessed by personal interviews conducted by an occupational hygienist. Exposures within 5 years prior to diagnosis of each matched case were ignored, both for the cases and their matched controls. The estimated relative risks for definite or probable exposure to chlorinated phenoxy compounds or chlorophenols for at least 1 day were 1.0 (95% confidence interval (CI): 0.3-3.1) for soft tissue sarcoma and 1.5 (95% CI: 0.6-3.7) for malignant lymphoma. When the criterion for exposure was raised to more than 30 days, the estimated relative risks were 2.0 (95% CI: 0.5-8.0) for soft tissue sarcoma and 2.7 (95% CI: 0.7-9.6) for malignant lymphoma. Additional analyses were carried out for exposure of at least 1 day to phenoxy herbicides alone or chlorophenols alone. None of the estimated relative risks was significantly greater than unity.

Cancer mortality in workers exposed to chlorophenoxy herbicides and chlorophenols

Epidemiological studies have revealed an increased risk of cancer, notably soft-tissue sarcomas and non-Hodgkin's lymphomas, in people occupationally exposed to chlorophenoxy herbicides, including those contaminated by 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD). We report here a historical cohort study of mortality in an international register of 18,910 production workers or sprayers from ten countries. Exposure was reconstructed through questionnaires, factory or spraying records, and job histories. Cause-specific national death rates were used as reference. No excess was observed in all-cause mortality, for all neoplasms, for the most common epithelial cancers, or for lymphomas. A statistically non-significant two-fold excess risk, based on 4 observed deaths, was noted for soft-tissue sarcoma with a standardised mortality ratio (SMR) of 196 and 95% confidence interval (Cl) 53-502; this was concentrated as a six-fold statistically significant excess, occurring 10-19 years from first exposure in the cohort as a whole (SMR = 606 [165-1552]) and, for the same time period, as a nine-fold excess among sprayers (SMR = 882 [182-2579]). Risks appeared to be increased for cancers of the testicle, thyroid, other endocrine glands, and nose and nasal cavity, based on small numbers of deaths. The excess of soft-tissue sarcomas among sprayers is compatible with a causal role of chlorophenoxy herbicides but the excess does not seem to be specifically associated with those herbicides probably contaminated by TCDD.

A meta-analysis of exposure to phenoxy acid herbicides and chlorophenols in relation to risk of soft tissue sarcoma

This analysis combines the results of the epidemiologic studies which appeared in the literature from 1979-1987 concerning the associations between phenoxy acid herbicides (PH) and chlorophenols (CP) and the occurrence of soft tissue sarcoma. Cohort studies and case-control studies are considered separately. After specifying criteria for inclusion, the total number of deaths due to cancer occurring in selected cohorts of people exposed to PH or CP was determined. The proportion of soft tissue sarcoma cases observed versus expected in the cohort studies, calculated using United States SEER registry data, resulted in a proportional mortality ratio of 3.5 (95% confidence interval of 0.7-10.3). Excluding the initial reports, the selected case-control studies had homogeneous risk estimates with a summary odds ratio of 1.1 (95% confidence interval of 0.9-1.4). Other attempts to assess the combined data did not yield results indicating an association. These meta-analyses do not provide strong support for an association between the specified herbicides and soft tissue sarcoma.

Soft tissue sarcoma and occupational exposures

The associations between soft tissue sarcoma (STS) and occupational exposures were studied in a case-referent study in the southeast of Sweden. Exposure information was obtained through mailed questionnaires to 96 cases, 450 randomly selected population referents, and 200 cancer referents. Odds ratios (OR), were calculated for various occupational groups, and particularly, for occupations with potential exposure to chlorinated phenoxy herbicides and chlorophenols. In the analyses based on population referents, increased risks for soft tissue sarcoma were seen for especially gardeners (OR = 4.1), but also railroad workers (OR = 3.1); construction workers with exposure to impregnating agents (OR = 2.3), asbestos (OR = 1.8), or pressure impregnating agents (OR = 1.7); and unspecified chemical workers with potential exposure to phenoxy herbicides and/or chlorophenols (OR = 1.6). A similar pattern appeared when cancer referents were used although the numerical values of the odds ratios became different. A grouping of jobs resulted in Mantel-Haensel OR from 1.5 to 1.9 for farmers and forestry workers, dependent on referents used and even more increased OR for railroad workers and unspecified chemical workers with potential exposure to phenoxy herbicides and chlorophenols. The results of the study confirm rather than refute that phenoxy herbicides and chlorophenols could be of etiologic importance for STS; the high risk for gardeners, although based on a small number of individuals, was unexpected and remains unclear. Also, since other cancers were used as referents, no definite problems of recall bias should obtain in this material. None of the exposed groups had a higher proportion of smokers than the unexposed group.

Pentachlorophenol-associated aplastic anemia, red cell aplasia, leukemia and other blood disorders

Aplastic anemia, pure red cell aplasia, leukemia, lymphoma and other hematologic disorders have followed exposure to products containing the pesticide pentachlorophenol (PCP). Information in a 25-year compilation of documented case reports is summarized, involving industrial and home exposure and accidental poisoning in a nursery. The potential hematologic, mutagenic and carcinogenic effects of PCP and its dioxin-dibenzofuran contaminants also are reviewed. Owing to widespread contamination of the environment by PCP products, and latent periods of up to several decades after exposure before these disorders become manifest clinically, it is necessary to consider their etiologic or contributory role. These issues continue to surface in toxic tort litigation relative to causation.

Phenoxy acid herbicides and contaminants: description of the IARC International Register of Workers. IARC Working Group

An International Register of Persons Exposed to Phenoxy Herbicides and Contaminants was established in 1984 by the International Agency for Research on Cancer in collaboration with the National Institute of Environmental Health Sciences (U.S.A.). The purpose of this Register is to investigate the long-term hazards associated with exposure to these herbicides and to serve as a system of scientific collaboration at the international level. Presently, 18,972 workers from 19 cohorts in 10 countries are enrolled in this Register. Fifteen cohorts are from companies that manufacture and formulate phenoxy acids or chlorophenols, and four cohorts are sprayers of phenoxy herbicides. Cancer incidence and mortality are the main outcomes of interest, and vital status for members of the Register has periodically been updated. The great advantage of this Register is its large size, facilitating the detection of hazardous effects of exposure.

Chloracne associated with employment in the production of pentachlorophenol

To evaluate the association between exposure to pentachlorophenol (PCP) and the occurrence of chloracne, we studied the medical and personnel records for individuals employed in the manufacturing of PCP. Forty-seven cases of chloracne were identified among 648 workers (7.0%) assigned to PCP production at a single plant between 1953 and 1978. The annual incidence rate varied considerably, ranging from 0 (in 1953) to 1.46 (in 1978). No linear trend in the risk of chloracne was observed with the duration of employment in the pentachlorophenol department. Workers with a documented episode of direct skin contact with PCP had a significantly increased risk of chloracne compared with workers who did not have a documented episode of direct skin contact (cumulative incidence ratio = 4.6; 95% confidence interval 2.6-8.1). Our results confirm that chloracne is associated with exposure to PCP contaminated with hexachlorinated, heptachlorinated, and octachlorinated dibenzo-p-dioxins and dibenzofurans.

A comparison of exposure estimates by worker raters and industrial hygienists

The validity and reliability of nine senior sawmill workers' estimates of frequency, duration, and routes of exposure were compared with individual workers' ratings of their own job titles and industrial hygienists' ratings of all job titles in the plant. The reliability of the senior workers' mean exposure estimates [group intraclass correlation coefficient (ICC) = 0.71] compared favorably with those of three pairs of hygienists (group ICC = 0.57, 0.67, and 0.81). The validity of their ratings was assessed in a comparison with urinary chlorophenate measurements representing 92% of the job titles in the sawmill. The senior workers' ratings [coefficient of determination (R2) = 0.22] resembled those of two pairs of industrial hygienists (R2 = 0.24, 0.22) and was significantly greater than that of the third pair (R2 = 0.08). The validity of the self-reports was also low (R2 = 0.15), but the difference was not statistically significant. Senior workers' exposure ratings appear to be as effective as the other methods tested.

Cancer incidence of workers in a Finnish sawmill

The cancer incidence of 1,223 sawmill workers with continuous employment of at least one year between 1 January 1945 and 31 December 1961 was followed until 31 December 1980. Separate analyses were made for the 801 workers hired after 1 January 1945, and smoking habits were surveyed. Among the men, 90 cases of primary cancer were detected versus 83.5 expected and among the women 55 cancer cases versus 44.5 expected. Skin cancer was in excess among the men, especially among those employed after 1 January 1945. Lip, mouth, and pharynx cancer and lymphomas were also slightly in excess among the men, as was leukemia among both sexes. Workplace exposure, especially to chlorophenols, may be associated with the excess skin cancer and the slight excess of lymphomas, but this finding should be further evaluated with special emphasis on well-defined exposure data.

Radicals involved in photoallergen/protein interactions

Aqueous solutions (pH = 8) of both 3,3'-dimethyl and 4,4'-dimethyl substituted analogues of the photoallergen fentichlor (bis(2-hydroxy-5-chlorophenyl)sulphide) produced stable semiquinone radicals when irradiated with u.v. light (greater than 310 nm). These radicals have been characterised using electron spin resonance techniques: the results confirm the assignment of hyperfine coupling constants for the parent fentichlor radical. The binding of fentichlor to HSA was found to be partly oxygen dependent demonstrating a role for semiquinone type radicals in the binding mechanism. The stoichiometry and specificity of the binding of the dimethyl analogues to soluble proteins were found to be similar to that of fentichlor itself.

Pentachlorophenol and the peripheral nervous system: a longitudinal study in exposed workers

A longitudinal study was performed to examine whether chronic occupational exposure to pentachlorophenol (PCP) or its compounds causes measurable alterations in the conduction velocity in peripheral nerves as an "adverse effect." In total, the results of nerve conduction velocity (NCV) determinations in 1980 and 1984 in 10 subjects (7 men, 3 women) who had been exposed for an average of 16 years (range 4-24) were available. The concentrations of PCP in the air at the workplace varied between 0.3 and 180 micrograms/m3 and were thus below the maximum allowed concentration (MAK value) of 500 micrograms/m3. The biological monitoring carried out showed the following results: PCP in the serum: 38-1270 micrograms/l; PCP in the urine: 8-1224 micrograms/l. Compared with the upper normal limits (PCP in the serum 150 micrograms/l, PCP in the urine 60 micrograms/l), distinct internal exposure to PCP has resulted in some of the employees. Determinations of the NCV of motor and sensory nerve fibres (ulnar, median, peroneal, and sural nerve) were always in the normal range. A significant difference in the NCV for the period 1980-4 could not be detected. In addition, the correlation analyses did not show any hints of "dose-effect relations." It is concluded that occupational exposure to PCP over several years in the concentrations observed probably do not lead to any adverse effects on the peripheral nervous system.

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

A cytogenetic study was performed on 20 healthy workers exposed to pentachlorophenol (PCP) in concentrations ranging from 1.2 to 180 micrograms/m3 (Maximum Concentration at the workplace is 500 micrograms/m3) for 3 to 34 years. PCP was determined in the blood plasma of all probands, yielding concentrations between 23 and 775 micrograms/l (Biological Tolerance Value is 1000 micrograms/l). In vitro PCP up to 90 mg/l was added to phytohaemagglutinin stimulated lymphocytes of normal healthy donors without any effect on sister chromatid exchange (SCE) or chromosomal aberrations (CA), whereas a slowdown of cell proliferation could be detected in the presence of 60 mg PCP/l. In vivo we neither observed a relation between PCP concentrations and the number of SCE nor an increase of CA.

Case-control study of multiple myeloma and farming

A previous case-control study which utilised the occupational information available on the New Zealand Cancer Registry found an increased risk of multiple myeloma in agricultural workers consistent with previous findings in the United States. The findings are now presented for the second phase of the study which involved interviewing 76 cases of multiple myeloma (who had been included in the previous study) together with 315 controls with other types of cancer. The previous finding on an excess of farmers in the case group was confirmed by the interview data (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.04). There were no significant differences between cases and controls regarding potential exposure to phenoxy herbicides or chlorophenols. There were also no significant differences regarding activities involving potential exposure to other agricultural chemicals, although the odds ratio for fencing work, which may involve exposure to arsenic and sodium pentachlorophenate, was 1.6 (95% confidence limits 0.9-2.7, P = 0.11). The odds ratios were significantly elevated for sheep farming (odds ratio = 1.9, 95% confidence limits 1.0-3.6, P = 0.04) and exposure to beef cattle (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.05). The odds ratio was also elevated for persons reporting a history of hay fever (odds ratio = 1.9, 95% confidence limits 1.0-3.5, P = 0.05). Overall, these findings suggest that the search for the causes of elevated mortality in farmers from multiple myeloma should be directed to potential causes other than pesticide exposure.

Chloracne from pentachlorophenol-preserved wood

A patient is presented who developed chloracne after exposure to lumber which was pressure-treated with pentachlorophenol (PCP). It was presumed that his disease arose via percutaneous absorption of polychlorinated aromatic compounds (dioxins and furans) which are known to contaminate technical grade PCP. The patient's condition improved after treatment with oral isotretinoin.

Non-Hodgkin's lymphoma and exposure to phenoxyherbicides, chlorophenols, fencing work, and meat works employment: a case-control study

A previous case-control study which used the occupational information available on the New Zealand Cancer Registry found that agricultural workers were at increased risk of developing non-Hodgkin's lymphoma. The findings are now presented for the second phase of the study which entailed interviewing 83 cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases together with 168 controls with other types of cancer and 228 general population controls. The findings for the two control groups were similar, and there were no significant differences between cases and controls regarding potential exposure to phenoxy-herbicides (odds ratio = 1.4, 90% confidence limits 0.7-2.5, p = 0.26) or chlorophenols (odds ratio = 1.3, 90% confidence limits 0.6-2.7, p = 0.39). The odds ratio for fencing work, necessitating exposure to several potential risk factors including arsenic and sodium pentachlorophenate was 2.0 (90% confidence limits 1.3-3.0, p = 0.01). The odds ratio for employment in a meat works, necessitating potential exposure to 2, 4, 6-trichlorophenol and zoonotic viruses, was 1.8 (90% confidence limits 1.1-3.1, p = 0.04). There was a significant statistical interaction between the risks associated with these two activities, the odds ratio for involvement in both activities compared with involvement in neither being 5.7 (90% confidence limits 2.3-14.3, p = 0.03).

Assessment of pentachlorophenol toxicity in newborn calves: clinicopathology and tissue residues

Newborn Holstein bull calves were fed either analytical pentachlorophenol (aPCP) or technical pentachlorophenol (tPCP) for 6 wk to establish and compare the clinical and pathologic manifestations of toxicity. Four groups of three calves/group were each fed either 1 or 10 mg X (kg body weight)-1 X d-1 of either aPCP or tPCP. A fifth group served as control. Dosages of both PCP preparations were normalized to contain equal concentrations of PCP. Toxic effects were observed only at the 10 mg/kg dose in the tPCP-treated calves. These effects included decreased body weight gain, anorexia, decreased serum protein concentration, elevated serum gamma glutamyl transferase, and decreased triiodothyronine (T3) and thyroxine (T4) concentrations. Histologic lesions included cortical atrophy in the thymus and squamous metaplasia and hyperkeratous changes in the Meibomian gland of the eyelid. Thyroid function, which was assessed in vivo by measuring the rate of T3 and T4 production over 4 h after thyrotropin-releasing hormone (TRH)-challenge, was not impaired suggesting an extrathyroidal site of toxic action. Although serum chemistry indicators were suggestive of hepatic injury there were no discernable lesions. Organ weight analyses were inconclusive but there was a tendency toward enlargement of liver, kidneys and thyroid and decreased weight of lungs, spleen and thymus. A toxic effect clearly related to PCP and not its contaminants was depressed active transport of p-aminohippurate measured in kidney slices in vitro. Steady state concentrations of PCP in serum were about 40 and 90 ppm for the 1 and 10 mg/kg groups, respectively. Concentrations of PCP among the major organs were comparable.

A follow-up study of cancer incidence among workers in manufacture of phenoxy herbicides in Denmark

The purpose of this cohort study is to shed further light on the potential carcinogenic effect indicated by a Swedish case control study of the 2,4-dichlorophenol and 4-chloro-ortho-cresol based phenoxy herbicides, unlikely to be contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). In the present study it was the intention to include all persons employed in manufacture of phenoxy herbicides in Denmark before 1982. The predominant product was MCPA and only a very limited amount of 2,4,5-T was processed in one of the two factories included in the study. Registration of the cohort was based on company records, supplemented with data from a public pension scheme from 1964 onwards. Ninety-nine percent of registered employees could be followed up. Cancer cases were identified by linkage with the National Cancer Register. Totals of 3,390 males and 1,069 females were included in the study. In the analysis special attention was given to soft tissue sarcomas (STS) and malignant lymphomas (ML) which are the diagnostic groups indicated to be associated with exposure to phenoxy herbicides in the Swedish studies. Five cases of STS were observed among male employees in contrast to 1.84 expected cases. This result supports the Swedish observation of an increased risk of STS following exposure to phenoxy herbicides unlikely to be contaminated with 2,3,7,8-TCDD. However, several potential biases have to be taken into account in interpretation of this observation and these are discussed. Seven cases of ML were observed among male employees in contrast to 5.37 expected which does not support the Swedish observation of an excess risk. The total cancer risk among persons employed in manufacture and packaging of phenoxy herbicides was equivalent to the cancer risk in the Danish population. Among males thus employed 11 lung cancer cases were observed in contrast to 5.33 expected. Attention should be given to exposure to spray dried MCPA-sodium salt in the plants, but other work place exposures and tobacco consumption may have contributed to the increased risk. The tabulation of data by many diagnostic groups may explain the excesses observed for rectum cancer among males and cervical cancer among females. The study has revealed that several potential biases have to be taken into account when the Swedish observations are tested in other settings.

The mortality of boot and shoe makers, with special reference to cancer

The study describes the mortality of 5 017 men known to have been employed in the boot and shoe manufacturing industry in three towns in Great Britain in 1939. At the end of 1982, 97.5% of the men were traced, and 3 434 (68.4%) were known to be dead. Expected numbers were calculated according to the person-years method and were adjusted according to the standardized mortality ratios of the counties in which the towns were situated. The mortality experience of the men for all causes, all cancers combined, and all other causes was favorable. The anticipated excess of deaths from nasal cancer (10 observed, 1.87 expected) was found, and the excess was significant for workers in the finishing room. Deficits were found for other types of respiratory cancer. An excess mortality from leukemia was found for workers in one town (7 observed, 3.0 expected), and the excess was significant for workers in the lasting and making room, where glues and solvents, including benzene, were known to have been used. An excess mortality from rectal cancer was found for workers in two towns (61 observed, 47.6 expected), and it was significant for workers in the lasting and making rooms (25 observed, 12.4 expected). Some supporting evidence for a risk of rectal cancer in this industry was found in the literature.