Phenoxy exposure

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Hardell L, Eriksson M, Lenner P, et al. 1981. Malignant lymphoma and exposure to chemicals, especially organic solvents, chlorophenols and phenoxy acids A case-control study. Br J Cancer 43 169-176. 

Data from Hardell, L. 1983. Epidemiological studies on soft-tissue sarcoma, malignant lymphoma, nasal and nasopharyngeal cancer, and their relation to phenoxy acid or chlo-rophenol exposure. Pages 367-374 in G. Choudhary, L.H. Keith, and C. Rappe (eds.). Chlorinated Dioxins and Dibenzofurans in the Total Environment. Butterworth, Woburn, MA. 

M Studies on phenoxy acid herbicides. I. Field Study Occupational exposure to phenoxy acid herbicides (MCPA, Dichloro-prop, Meco-prop, and 2,4-D) in agriculture. Arch Toxicol 1983... 

The presence of TCDD in 2,4,5-T is believed to be largely responsible for other human toxicities associated with the herbicide. There is epidemiologic evidence indicating an association between occupational exposure to the phenoxy herbicides and an excess incidence of non-Flodgkin s lymphoma. The TCDD contaminant in these herbicides seems to play a role in a number of cancers such as soft tissue sarcomas, lung cancer, Flodgkin s lymphomas, and others. 

When these three cancers (soft-tissue sarcoma, non-Hodgkin s leukemia, and Hodgkin s disease) are considered as a whole, it is noteworthy that the strongest evidence for an association with exposure to phenoxy herbicides is the series of case-control studies conducted by Hardell [Lennart Harden, a Swedish physician] and colleagues and the cohort studies of herbicide applicators and agricultural workers.25 26... 

According to the 1990-93 CAREX database for 15 countries of the European Union (Kauppinen et al., 1998) and the 1981-83 National Occupational Exposure Survey (NOES) in the United States (NOES, 1997), approximately 45 000 workers in Europe and as many as 27 000 workers in the United States were potentially exposed to pentachlorophenol (see General Remarks). Recent figures give rough estimates of 500 pentachlorophenol-exposed workers in wood treatment facilities in the United States (Norman, 1998). No current data on numbers of workers exposed to other chlorophenols were available. Occupational exposures to chlorophenols have occurred in their production, in the production and use of some phenoxy acid herbicides, in sawmills and other wood-related industries, the textile industry and tanneries. Occupational exposures to penta-... 

Associations with chlorophenols were, however, analysed in two case-control studies nested within 24 of the 36 cohorts of the lARC study. These compared 11 cases of soft-tissue sarcoma and 32 cases of non-Hodgkin lymphoma with 55 and 158 controls, respectively (Kogevinas et al., 1995). Exposure to chlorophenols, phenoxy acid herbicides, dibenzodioxins and -furans and other agents was assessed by a team of industrial hygienists (Kauppinen et al., 1994). Odds ratios for non-Hodgkin lymphoma, not adjusted for exposure to other agents, were 1.3 (95% CI, 0.5-3.1) for any chlorophenol, 2.8 (0.5-17.0) for pentachlorophenol and 1.0 (0.3-3.1) for 2,4-dichlorophenol. No excess risk was found in relation to other chlorophenols, but the munber of exposed cases was small. The odds... 

Exposures to chlorophenols and their salts have occurred in their production, in the production of some phenoxy acid herbicides, in the wood industry, the textile industry and tanneries. They have been detected at low levels in ambient air and water. 

Harden, L., Johansson, B. Axelson, O. (1982) Epidemiological study of nasal and nasopharyngeal cancer and their relation to phenoxy acid or chlorophenol exposure. Am. J. ind. Med., 3, 247-257... 

Kauppinen, T.P., Pannett, B, Marlow, D.A. Kogevinas, M. (1994) Retrospective assessment of exposure through modelling in a study on cancer risks among workers exposed to phenoxy herbicides, chlorophenols and dioxins. Scand. J. Work Environ. Health, 20, 262-271... 

D absorbed is excreted in the urine and because dermal exposure is considered the most likely exposure route ( 1, 2,3). Excretion studies on phenoxy herbicides in man (J3-6) show that 90% of the 2,4,5-T and 75% to 95% of the 2,4-D was excreted unchanged... 

In humans, 2,4-D in large doses can cause coma and generalized muscle hypotonia. Rarely, muscle weakness and marked myotonia may persist for several weeks. With 2,4,5-T, coma may occur, but the muscular dysfunction is less evident. In laboratory animals, signs of liver and kidney dysfunction have also been reported. There is limited evidence that occupational exposure to phenoxy herbicides is associated with an increased risk of non-Hodgkin s lymphoma the evidence for soft-tissue sarcoma, however, is considered equivocal. 

The extent to which exposure to pesticides may be hazardous to applicators depends upon exposure levels and the toxicity of the compounds. The phenoxy herbicides have been used for nearly 40 years, and no injury to workers properly using these herbicides has been clearly established. 

In spite of their record of producing no detectable harm to humans, the phenoxy herbicides 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) have acquired a less than desirable reputation. This reputation has been the result of their association with low levels of impurities. They have commonly been used as a mixture, which contains trace amounts of highly toxic 2,3,7,8-tetrachlorodibenzo-jj-dioxin, a minor product in the manufacturing of 2,4,5-T. In early production of 2,4,5-T a low level of dioxin was retained. Today s manufacturing process produces 2,4,5-T with no more than 0.1 ppm of the 2,3,7,8 tetrachlorodibenzo-]D-dioxin. This association with toxic dioxin and confusion of the public and the media regarding these issues have led to public distrust in the safety of using phenoxys and to the need to establish clearly the extent of human exposure to these compounds as well as the resulting effects of this exposure. 

Inadequate pre-exposure information. Although workers fill out questionaires indicating that they have not used phenoxy herbicides during the previous two weeks, sometimes these workers come into the study with positive background levels of phenoxy in their urine. 

The source of the exposure either before or after the actual spray date appears to be related to some contact with the phe-noxys of which the crewmember was not aware. Possible avenues of re-exposure include wearing phenoxy contaminated clothing on days other than the planned spray day, i.e., gloves, boots, pants, shirts, or chaps. Workers may also have received some exposure from their phenoxy application equipment. This may occur if a worker has a spray operation scheduled and wants to clean or check his equipment in advance. Another potential source of exposure is the vehicles in which the workers ride. Often workers, pesticide concentrate, empty containers, and equipment are hauled in the same pick-up truck or van. 

Due to our awareness that extraneous exposure can occur, we have taken measures to limit these types of pre-exposure in our most recent studies. The data we have collected supply adequate evidence that extraneous means of exposure are common. If it occurs in these phenoxy studies, it is likely that it occurs for workers applying more toxic pesticides. 

Including this extraneous exposure, the degree of safety that we calculated for forest workers using phenoxy herbicides was such that even the most highly exposed crewmembers received exposure which was several orders of magnitude below the noobservable-effect-level. Decreases in the level of exposure with the use of protective measures, however, may be of real consequence to workers applying more toxic materials. 

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