This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization.

Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization World Health Organisation Geneva. The International Programme on Chemical Safety (IPCS) is a Joint venture of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization.

The main objective of the IPCS is to carry out and disseminate evaluations of the effects of chemicals on human health and the quality of the environment. Supporting activities include the development of epidemiological, experimental laboratory, and risk-assessment methods that could produce internationally comparable results, and the development of manpower in the field of toxicology. Other activities carried out by the IPCS include the development of know-how for coping with chemical accidents, coordination of laboratory testing and epidemiological studies, and promotion of research on the mechanisms of the biological action of chemicals.

The World Health Organization welcomes requests for permission to reproduce or translate its publications, in part or in full. Applications and enquiries should be addressed to the Office of Publications, World Health Organization, Geneva, Switzerland, which will be glad to provide the latest information on any changes made to the text, plans for new editions, and reprints and translations already available. (c) World Health Organization Publications of the World Health Organization enjoy copyright protection in accordance with the provisions of Protocol 2 of the Universal Copyright Convention.

All rights reserved. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters.

The illness most frequently observed in workers engaged in the manufacture of trichlorophenol, 2,4,5-T, and related products is a skin disease called chloracne. This skin disease has also been called "Pernakrankheit" (perchlorinated naphthalene illness or halogen wax acne) and was described by Herxheimer (1899). In addition to the halogenated phenols, chloracne is caused by a number of chlorinated compounds such as the chlorinated biphenyls and chlorinated naphthalenes (Muller, 1937; Braun, 1955; Crow, 1970; Kimbrough, 1974).

Although chloracne is well known to those engaged in the treatment of occupational diseases, many outbreaks that have occurred over the years, particularly in the USA, have not been reported in the scientific literature. In the Federal Republic of Germany, chloracne is now considered an occupational disease for which compensation is mandatory (Braun, 1970).

Herxheimer (1899) also described general toxic signs and symptoms in his patients, such as lack of appetite, weight loss, headache, and vertigo. After his original observations and publication, several other reports followed. The technique of obtaining chlorine gas consisted of an electrolytic procedure where a mixture of potassium, sodium, and magnesium chlorides was subjected to a current with a central carbon electrode where the chlorine was obtained and piped off. The workers who took care of the chlorine gas never developed chloracne thus refuting the original hypothesis by Herxheimer.

By contrast, those who handled the electrodes and cleaned the reaction vessels were those afflicted with chloracne. Already at this time chlorinated phenolic compounds were considered as possible noxious agents (Fraenkel, 1902). This however could never be proven and even at present, when satisfactory analytical techniques are now available, no analysis of the so-called "tuffy tar" has been carried out.

Another class of chlorinated organic compounds causing skin damage appeared during the First World War (1914-1918). At this time perchlorinated naphthalenes had come into use as insulation materials, e.g., in the radio and electronic industry. The first description of Pernakrankheit was that by Wauer (1918). The use of the unspecified technical mixture of chlorinated naphthalenes spread all over the world and caused numerous intoxications notably among workers in manufacture. The perna disease has been summarized by von Wedel et al. (1943) and described in particular detailed by Braun (1955). Apart from chloracne the systemic effects of the same compounds have been dealt with by Drinker et al. (1937) and Greenburg et al. (1939).

Both in man and experimental animals, serious liver damage occurred after exposure to chlorinated naphthalenes, consisting of liver necrosis and toxic jaundice (acute yellow liver atrophy). Among several hundred cases of chloracne due to these compounds, Braun (1955) tabulated 24 deaths due to toxic jaundice and 14 recoveries. It should be pointed out that a fulminant liver disease with jaundice of this kind is an extremely rare condition. For comparison, it has never occurred after exposure to trichlorophenol (TCP) and TCDD as described below.

Note should also be taken of the fact that not only were the perchlorinated naphthalenes an ill identified mixture of chemical species, but exposure frequently occurred at the same time to mixtures of chlorinated biphenyls, the latter now known to be contaminated with chlorinated dibenzofurans. The potentiation of toxicity by these mixtures and other chlorinated compounds were discussed by Drinker et al. (1937), Greenburg et al. (1939), von Wedel et al. (1943), and Risse-Sunderman (1959).

Several accidental ingestions of chloracnegenic compounds have occurred. They are of particular importance in relation to discussions on whether chloracne is a systemic or local disease. The so-called Yusho disease is discussed in section 11. Herzberg (1947) described several cases of chloracne, in which other toxic signs and symptoms were seen, due to consumption of "chlorinated paraffin" used as a substitute for butter during cooking in postwar Berlin.

Among general signs and symptoms observed were gastrointestinal disturbances with abdominal pain, headache, pain in joints, neuropathy, depression, and lack of appetite. The dermatological symptoms were erythema, exanthema, comedones, and retention cysts in sebaceous glands. It was noted as remarkable that the skin signs had a follicular predilection, as in seborrhoea (face, head, bosom, and back).

The slow development of chloracne, and particularly the fact that the sebaceous glands were affected, led the author to conclude that it was a secretory disease(Ausscheidungstoxikose). With regard to the chloracnegenic component, it is unlikely that paraffin itself was active. Herzberg speculated that something else, possibly a pyrolysis product that arose during cooking, could have caused the disease.

The first reported intoxication with a mixture probably containing TCDD, although the chemical structure was not given, occurred in February 1910. Five people were said to have been contaminated after a reactor explosion and two of these were described in some detail in a dermatological thesis (Teleky, 1913; Wahle 1914). Wahle (1914), however, in his thesis emphasized that this intoxication was not due to any of the chlorinated naphthalene derivatives that were well known by then.

An industrial poisoning was reported in 1949, due to the formation of TCDD in uncontrolled exothermic reactions occurring during the manufacture of TCP at a 2,4,5-T-producing factory in Nitro, West Virginia, USA. The temperature in one of the reactors containing tetrachlorobenzene, methanol, and sodium hydroxide increased, a relief valve opened, and the contents of the vessel were discharged into the interior of the building and over a wide area outside of the building.

A total of 228 people were affected. Symptoms included chloracne, nausea, vomiting, headaches, severe muscular aches and pains, fatigue, emotional instability, and intolerance to cold. Laboratory findings showed an increase in total serum lipids and an initially prolonged prothrombin time. Among those affected were not only workmen, but also laboratory personnel, medical personnel, and even the Safety Director who visited the area of exposure. Several wives who had never visited the plant also developed acne, usually at the same time as their husbands working at the plant.

A man from the nearby town who purchased a truck that was parked in the vicinity of the accident at the time it occurred, and his child, also developed chloracne. The disabling symptoms, which kept men from their jobs for as long as 2 years, were severe aches and pains and fatigability, the manifestations of peripheral neuropathy. Liver tests 4 years later were normal, but mild cases of acne were common. TCDD was still an unknown chemical. The follow-up to this accident will be discussed in section 8.4.

In 1953, at the Badische Anilin and Soda Fabrik, during the alkaline hydrolysis of 1,2,4,5-tetrachlorobenzene to 2,4,5-trichlorophenol, the temperature and pressure in an autoclave increased rapidly and resulted in an exothermic reaction releasing a great deal of steam through a safety valve of the reaction vessel. This steam covered the walls, windows, doors, and machinery in the rooms of four floors, and finally precipitated in solid form on everything in these rooms.

Forty-two workers involved in the clean-up operations developed chloracne, and even after the extensive clean-up operations occasional workers still developed chloracne. Thereafter the autoclaves were used for 2 years without incident but in 1958 a mechanic who conducted repair work on an autoclave subsequently developed chloracne (Hofmann, 1957; Goldmann, 1972). In 1968 and 1969 the building containing the autoclaves was dismantled.

Goldmann (1972, 1973) conducted a study of the 42 workers exposed in this accident. In 21 cases, the chloracne was preceded by a non-specific dermatitis and in two cases very persistent chronic conjunctivitis and blepharitis were observed; 14 cases also showed involvement of other organs. In four instances the liver was affected, and microscopic examination of the liver again showed a very characteristic grey pigment that did not stain positive for iron.

A transient involvement of the myocardium was also noted. In five instances the upper respiratory tract was involved with tracheitis and bronchitis. There was one instance of haemorrhagic pleuritis and one instance of afebrile gingivitis and stomatitis. In a number of cases a high susceptibility to infection was noted, sometimes accompanied by a decrease in gamma-globulin. One worker died of pancreatitis, in seven cases the central nervous system was affected, three instances of toxic polyneuritis were recorded, and in two instances hearing, sense of smell, and taste were impaired. The child of one of these workers also developed chloracne, and in most of the workers active chloracne persisted for many years - in one instance for 18 years. Follow-up studies are described in section 9.4.

Of particular interest is a study by Risse-Sundermann (1959). According to oral reports by the treating physician, all 24 members of a team working in a trichlorophenol operation became ill after the production process was switched to the pressurized phenol process in the spring and summer of 1954. Slightly different acneiform skin conditions appeared as symptoms of the toxic exposure. In addition, the patients suffered from dizziness, nausea, vomiting, lacrimation, burning of the eyes, difficulty in hearing, gastrointestinal spasms, intolerance to fatty foods, diarrhoea, jaundice, hepatitis (which was fatal in one case), and paresthesias and hyperesthesias, as well as extreme irritability. One patient became psychotic and committed suicide. In addition, some of the patients complained of impotence. Ten workers at this chemical factory were followed for five years by Risse-Sundermann (1959).

In addition to the signs and symptoms mentioned above, she noticed swollen lymph glands and a considerable decrease in body weight. The patients underwent neurological examination, with no objective signs being observable. Of particular interest in this well documented study is the fact that in three patients the general symptoms (e.g., tiredness, depression, lack of appetite, stomach pains, sexual dysfunction) preceded that of the skin manifestations .

Bauer et al. (1961) reported a study of workers affected by three different outbreaks of chloracne. In this study more than 100 workers were examined. Of these, 31 Hamburg workers had been exposed 5 years earlier. Nine were examined in detail and their symptoms tabulated. Initially, there was dermatitis and irritation of the face, sometimes accompanied by conjunctivitis, and followed by the gradual development of chloracne and patchy pigmentation of the skin. In some cases irritations of the mucous membranes of the face and upper respiratory tract, together with a persistent blepharoconjunctivitis, were also noted.

In the follow-up study, a number of cases of liver injury were observed and, at liver biopsy, a typical grey pigment was observed in liver sections, which did not stain positive for iron. Viral hepatitis was suspected. In a few cases, chronic bronchitis and occasional myocardial damage were also observed. In all cases, fatigue was the main complaint and muscle weakness and muscle pain were described by the workers, particularly in the proximal muscles of the lower extremities. All nine also reported decreased libido.

In a few instances, paresthesia and hyperesthesia or pronounced sensory neuropathy were observed, and minor circumscribed pareses were found. A psychovegetative syndrome occurred in most of the workers. Other signs recorded were: inability to concentrate, memory deficits, sleep disturbances, particularly increased somnolence, decreased drive, and alcohol intolerance. Psychological tests also showed abnormalities.

Following the malfunction of a reaction vessel in northern Italy, in which 2,4,5-trichlorophenol was produced, the temperature in the vessel increased rapidly and an intense black vapour filled the work-room covering everything with a black deposit. Five workers engaged in clean-up operations developed chloracne (Hofmann & Meneghini, 1962). None of those involved in the clean-up exhibited any involvement of general systemic toxicity (even after 16 months) that could be related to exposure to the tar and soot.

However, one 15-year-old worker developed folliculitis and superficial nodular elements on the face a few days after initial exposure. A slow but progressive generalization of the dermatosis developed on the trunk, scalp, and lower extremities. An examination several months later revealed no damage to the renal or liver parenchyma. However, this worker was found to still suffer from outbursts of chloracne in 1980 (Holmstedt, 1980).

Duverne et al. (1964) reported a case that occurred at a plant at Lyon, France, where products that used 2,4,5-tri-chlorophenol as a starting material were manufactured. This worker developed chloracne as well as serofibrinous pleuritis. Ten workers also developed chloracne at a plant near Grenoble,France, which produced 2,4,5-trichlorophenol that served as the starting material for phenoxy pesticides and germicides for cosmetics. These workers showed symptoms of systemic poisoning similar to those reported by Goldmann (1972), and hepatic insufficiency with lipaemia and elevated serum cholesterol levels (Dugois & Colomb, 1956). Another accident resulting in TCDD exposure of workers occurred in the same factory in 1966 (Dugois et al., 1967).

An exothermic reaction resulted in an explosion at a plant in Chesterfield, England, in 1968. The company made 2,4,5-trichlorophenolfrom tetrachlorobenzene and the explosion occurred during the process involving ethylene glycol and caustic soda under atmospheric pressure (Milnes, 1971). In this incident, 79 workers developed chloracne but there was no evidence of systemic illness (May, 1973). In 1971, 3 years after the explosion, two workers who had not been involved in the explosion or its aftermath were employed as pipe-fitters at a new installation, away from the site of the explosion, to refit one of the cleaned tanks.

They both developed severe chloracne, and the son of one of these workers and the wife of the other also developed this condition (Jensen & Walker, 1972). May (1973) cited two incidents involving explosions in a similar process. In the first incident, fatal injuries were recorded; in the second incident, all 50 exposed persons fell ill after 10 days and had liver injury.

In the USA, an outbreak of chloracne occurred among workers manufacturing 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid (Bleiberg et al., 1964); 29 workers developed chloracne and 11 of these had elevated urinary uroporphyrins and exhibited varying degrees of acquired porphyria cutanea tarda. At least one of these workers had abnormal liver-function tests and microscopic examination of a liver biopsy specimen showed parenchymal cell regeneration and haemofuscin pigment.

Many of the workers with chloracne showed hyperpigmentation of the skin. A second study of the workers at this plant was conducted in 1969 by Poland et al. (1971). A total of 73 male employees were examined, and moderate to severe chloracne was found in 13 workers (18%), mild chloracne in 35 (48%), hyperpigmentation in 30, and uroporphyrinuria in 1.

No definite systemic illness could be documented in these workers. Of those studied, 33 had been employed at the plant for 0-4 years, 10 for 4-8 years, and 30 for more than 9 years. The mean duration of employment was 8.3 ± 7.6 years (mean ± 1 SD). The trichlorophenol manufactured in this plant contained 10-25 mg TCDD/kg. Twenty-six of the workers seen by Bleiberg et al. (1964) were also seen in a follow-up study. Six months prior to the second survey (Poland et al., 1971), the manufacturing process was altered so that the 2,4,5-T produced contained less than 1 mg TCDD/kg.

In 1964, in the USSR, many workers developed chloracne while engaged in producing 2,4,5-T. Production was then discontinued (Telegina & Bikbulatova, 1970). On 10 July 1976, an explosion occurred at the ICMESA plant at Meda, near Seveso, Italy, when 12 workers were present. All 176 workers of the plant were examined 3 or 4 weeks after the accident. Chloracne was suspected in 1 of them; the others showed minor symptoms that could not be correlated with exposure.
 
Alkaline phosphatase and delta-glutamyltransferase seemed slightly increased in 32 and 37 cases, respectively, while five workers showed a reduction in their delta-aminolevulinic acid dehydratase blood levels, and three showed moderately increased urinary gamma-aminolevulinic acid (Zedda et al., 1976). Similar findings were reported by Fara et al. (1976) and Reggiani (1978). The follow-up of the general population is described in section 8.2.

8.2.1  Missouri, USA

USA Environmental exposures have occurred in a small area of Missouri, USA (Carter et al., 1975; Kimbrough et al., 1977; Kimbrough, 1984). In the summer of 1971 many birds, rodents, cats, dogs, insects, and horses died after exposure in a horse arena in eastern Missouri.

The incident followed the spraying of "waste oil" on the horse arena for dust control. Within 3 weeks of the spraying of this arena, two other arenas were sprayed. In all, 57 adult horses died, 26 abortions occurred among the horses at the most heavily exposed farm and many foals died soon after birth. At the time, the nature of the chemical that had caused the problem was unknown.

The arenas were excavated and the contaminated dirt dumped at other sites. After many fruitless attempts to identify the cause of this outbreak, it was discovered in 1973-1974 that the original soil from one of the arenas contained 5600-6500 mg trichlorophenol/kg, 31.8-33.0 mg TCDD/kg, and 1350-1590 mg polychlorinated biphenyls/kg. Because of this finding, the episode was reinvestigated. It was found that the salvage oil company that sprayed the three arenas routinely collected discarded motor oil and lubricants from over 2000 service stations in eastern Missouri and southwestern Illinois.

It also collected, from various sources, a limited amount of used organic solvents such as transformer oils and other compounds. A company in southwestern Missouri was finally identified as a source of TCDD. This company had manufactured trichlorophenol as an intermediate for hexachlorophene. The production of 2,4,5-tri-chlorophenol had generated a distillate residue which was emptied once a week into a residue storage tank. Initially this chemical waste was collected and incinerated but, in 1971 when the trichlorophenol producer experienced a financial crisis, he arranged for the chemical wastes to be disposed of by a chemical supplier.

The chemical supplier subcontracted the chemical waste disposal to the salvage oil dealer. The salvage oil dealer added the toxic chemical waste to his salvage oil storage tank, having collected a total of 18 000 gallons. This material, mixed with salvage oil and other chemicals, was sprayed on the riding arenas and some of it was taken to re-refining companies. Soil samples from arenas where contaminated dirt had been dumped in 1974 contained trichlorophenol levels that ranged from 1.5-32.6 mg/kg, TCDD levels that ranged from 0.22-0.85 mg/kg, and polychlorinated biphenyl levels that ranged from 10-25 mg/kg.

A 6-year-old girl, who had used one of the arenas for sandbox-like play in 1971, developed epistaxis, headache, diarrhoea and lethargy, haemorrhagic cystitis, and signs of pyelonephritis. She had an uneventful recovery. Three other females exposed to the same arena had recurring headaches, skin lesions, and polyarthralgias. Two 3-year-old boys in another arena developed chloracne on the exposed skin surfaces which lasted for more than a year. Evaluation of the three female patients 5.4 years after exposure to TCDD-containing oil showed them to be in good health (Beale et al., 1977).

A comprehensive medical examination of 154 residents exposed to TCDD, and 155 unexposed residents in similar type housing in eastern Missouri, revealed no consistent differences between the two groups. The examination included a medical history, physical examination, serum and urinary chemistries, and immunological and neurological tests. The findings may suggest that long-term TCDD exposure is associated with depressed cell-mediated immunity (decreased delayed-type hypersensitivity skin reactions to standard antigens) (Hoffman et al., 1986; Stehr et al., 1986). Urinary concentrations of glucaric acid were not significantly different between persons identified as being at high or low risk (Steinberg et al., 1985).

8.2.2 Seveso, Italy

The scientific follow-up on the population of Seveso, N. Italy, which had been accidentally exposed to TCDD in 1976 (see sections 4.1.1 and 8.1), was guided by an international steering group headed by Professor M.A. Klingberg. The group completed its work in February 1984 and concluded that "it is obvious that no clear-cut adverse health effects attributable to TCDD, besides chloracne, have been observed" (Regione Lombardia, 1984). A total of 193 people had displayed symptoms of chloracne, but at the beginning of 1984 only 20 presented active symptoms. After 15-20 days exposure to TCDD soil levels of 270-1200 µg/m2, there was a marked incidence of chloracne.

No disturbance of biochemical functions were seen when the exposure had been limited to soil with TCDD levels at or below 30-70 µg/m2. Later evaluations failed to confirm earlier findings of a decrease in motor nerve conduction velocity in some individuals. A significant increase in urinary glucaric acid levels, indicating increased microsomal enzyme activity, was found 3 years after exposure in 67 exposed children, as compared to 86 non-exposed children (Ideo et al., 1982, 1985). The steering group found the data difficult to evaluate as analytical and individual biological variabilities were not explained (Regione Lombardia, 1984).

Studies performed on the rate of spontaneous abortions and birth defects in the Seveso area do not allow any conclusions to be drawn (Tognoni & Bonaccorsi, 1982). The hypothesis that low exposure might cause pre-pregnancy or pregnancy effects that adversely affect the outcome was tested using several exposure models. The only finding was a slightly higher rate of haemangioma among newborns in the exposed group. However, this showed up only with one of the exposure models. It was considered doubtful that this was due to TCDD exposure (Regione Lombardia, 1984).

Lymphocytes from inhabitants of Seveso were examined for chromosomal aberrations by Regianni (1980a,b) and Mottura et al. (1981). In 17 TCDD-exposed individuals examined within two weeks of the accident, no increase in chromosomal aberrations was observed (Regianni, 1980). In the abstract by Mottura et al. (1981), chromosomal aberration analysis was performed on subjects distributed into three classes: acute exposure, chronic exposure, and a control group of non-exposed subjects. No significant difference in the frequency of chromosomal aberrations in the three exposure categories was reported. Data on number of subjects, chromosomal aberrations, and exposure level and time were not given.

Tenchini et al. (1983) published a comparative cytogenetic study on induced abortions from women exposed to TCDD after the Seveso accident, and in non-exposed subjects. Chromosome analysis was performed on maternal peripheral blood, placental and umbilical cord tissues, and fetal tissues. No significant differences were found in the level of chromosomal aberrations in the blood of placenta and umbilical cord from TCDD-exposed and non-exposed women. The exception was fetal samples from non-exposed women, in which a significant increase in chromosomal aberrations was obtained, possibly an artefact due to experimental techniques. The effect of TCDD on fetal chromosomes is therefore still unclear. Several epidemiological follow-up studies are continuing in and around Seveso.

8.2.3 Viet Nam

From 1960 to 1969 a mixture of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid (Agent Orange), which was contaminated with TCDD (concentrations ranging from 0.5 to 47 mg/kg) (Kearny et al., 1972), was sprayed over areas of Viet Nam as a defoliant. The spraying from 1960 to 1965 was minimal; in 1966 it covered slightly more than 800 000 acres, in 1967 almost 1.7 million acres, in 1968 over 1.3 million acres, and in 1969 1.2 million acres.

Studies have been carried out since the early 1970s to ascertain whether the exposure of the general population in Viet Nam to this herbicide could have resulted in an increased incidence of birth defects. However, the results of such investigations have not been published in readily available peer-reviewed journals, making it difficult to assess the scientific significance of the findings.

Such studies have been reviewed by Westing (1984) and Constable & Hatch (1985). Those studies reviewed indicate a range of effects including spontaneous abortions, infertility, and birth defects. However, there are marked deficiencies in experimental design in most, if not all, studies, including potential bias in the selection of populations, poor record-keeping of populations and biological effects, such as congenital malformations, and a lack of control over possible confounding factors. These deficiencies make it difficult, if not impossible, to use this body of data in assessing the human health risks from exposure to phenoxyherbicides contaminated with TCDD and other PCDDs.

Tung (1973) reported an increased incidence of liver tumours in Viet Nam. From 1955 to 1961 there were 159 cases of liver cancer out of a total of 5492 cancer cases, and from 1962 to 1968, 791 out of a total of 7911 cancer cases. Van (1984) continued Tung's investigation. Previous exposure to herbicides of 21 male cases of primary liver cancer and 42 controls was ascertained. Six of the 21 cases and three of the controls had lived or worked in areas sprayed with herbicides or had moved there shortly after spraying ceased. Residence time varied from 8 to 77 months. There is a lack of information on confounding factors and there was a chance for bias in these studies. In general, the possibility of exposure to multiple chemicals and the short latency period noted make the study by Van (1984) of little value for assessing risk (IARC, 1986).

In 1979, the United States Air Force (USAF) initiated an epidemiological study into the possible health effects from chemical exposure of Air Force personnel who conducted aerial dissemination of herbicide in Viet Nam (Operation Ranch Hand) (Lathrop et al., 1984). The purpose of this investigation was to determine whether long-term health effects exist and can be attributed to occupational exposure to herbicides. This study used a matched cohort design in a non-concurrent prospective setting, incorporating mortality, morbidity, and follow-up studies.

The report presented the results of health information on 2706 Ranch Handers and comparison individuals obtained by questionnaire and 2269 Ranch Handers and comparison individuals undergoing an extensive physical examination. It was concluded that there was insufficient evidence to support a cause and effect relationship between herbicide exposure and adverse health in the Ranch Hand group at this time. The study disclosed numerous medical findings, mostly of a minor or undetermined nature, that require detailed follow-up.

In a study of 15 soldiers in Australia exposed to Agent Orange, no increases in structural chromosomal aberrations or sister chromatid exchanges were noticed, compared to a control group of 8 subjects (Mulcahy, 1980). In 1980 the Australian Commonwealth Institute of Health agreed to conduct a series of scientific investigations into the health of Viet Nam veterans and their families. After considerating the most appropriate study programme, it was decided in 1981 to conduct, as part of that programme, a case-control study of congenital anomalies and Viet Nam service (Donovan et al., 1984). The report is largely negative, as is that of Erickson et al. (1984) which reported a similar study of American veterans.

Raised transaminase values  in blood              

Many signs and symptoms have been reported in studies of human exposures to PCDDs, both occupationally and from the general environment. These have been compiled from the various studies and are shown in Table 64.

8.3.1 Skin manifestations

Chloracne is a sign of exposure to several chlorinated cyclic organic compounds, the most potent being TCDD. Chloracne thus may serve as a marker of such exposure. The most distinctive lesion in chloracne is the so-called cyst, a skin-coloured elevation that may measure from 1 mm to 1 cm in diameter, with a central opening that may be difficult to detect. Comedones that contain black or black-appearing material in their openings are also present. There may be a secondary inflammatory reaction, melanosis, and hyperkeratosis, and these skin changes may be preceded by a "cable rash" or "cable itch".

These skin lesions resemble photosensitivity reactions and the bearers may suffer severe pruritus. Microscopic examination of the skin lesions shows marked dilatation of the hair follicles which are filled with keratinous material, the sebaceous glands may be partly or completely atrophied and, occasionally, hyperplasia of these glands has also been reported. Hyperkeratosis and acanthosis of the surrounding epidermis usually accompany these lesions.

Atrophy of the epithelium and thinning of the epithelial walls surrounding these keratinous cysts are observed at a later stage of the disease. If the follicular cysts rupture, foreign body granulomata may also be observed. Healing of these skin lesions usually results in deeply pitted scars. The distribution of chloracne is predominantly facial, affecting in particular the malar areas, the jaws, and the regions behind the ears. At times it may involve the ear canal and, with increasing severity, also the rest of the face and neck. In more extensive cases, the outer upper arms, neck, back, abdomen, outer thighs, and genitalia may also be involved (Crow, 1970).

While the absence of chloracne does not absolutely rule out exposure to TCDD, it usually indicates that there has been no exposure to a toxic dose of the substance. "Toxic" is used here to indicate both systemic and local effects. Where there has been exposure to TCDD and chloracne has resulted, it is the only known clinical sign that persists for a long period of time, even for the remainder of the exposed person's life time. In a large group of people exposed to mixtures containing TCDD, the absence of chloracne usually indicates that exposure to a toxic dose was unlikely and also makes it unlikely that severe, persistent systemic disorders will result.

Hyperkeratosis is a fairly common phenomenon whereas hyperpigmentation and hirsutism are rare. It should be noted that hyperkeratosis is prominent in the exposed Seveso children who have no affected sebaceous glands. These glands develop only at puberty. Elastosis of the skin has been noted as a long-term effect of TCDD exposure.

8.3.2 Systemic effects

Liver effects following exposure to PCDDs have been diagnosed even by histological examination, and account for temporarily raised transaminases in blood, hypercholesteraemia, and hypertriglyceridaemia. Bauer et al. (1961) and Risse-Sundermann (1959) do not however exclude viral hepatitis as a cause of such findings in their patients exposed to TCDD. Loss of appetite, weight loss, and digestive disorders are common complaints from humans exposed to either TCDD itself, or to technical mixtures containing TCDD. Muscular aches and pain and weakness in extremities have been reported, particularly after exposure to technical mixtures containing TCDD.

Swollen lymph nodes have also been reported, both after exposure to "pure" TCDD and to mixtures. The cardiovascular, urinary tract, respiratory, and pancreatic disorders reported are of doubtful significance with regard to a causal relationship to TCDD exposure.

Porphyria cutanea tarda has been reported in two cases of occupational exposure where chlorinated organic compounds were manufactured in addition to trichlorophenol. These were the incidents at the factory of Diamond Alkali, Newark, New Jersey, USA, in 1956 (Poland et al., 1971) and at Spolana, Czechoslovakia, between 1964 and 1969 (Pazerova-Vejlupkova et al., 1981). The porphyria cutanea tarda observed in these cases was very unlikely to have been induced by exposure to TCDD but rather by exposure to other chlorinated organic compounds manufactured in these plants (Jones & Chelsky, 1986).

8.3.3  Neurological effects

Sexual dysfunction (lack of libido and impotence) has been reported after acute exposure to both "pure" TCDD and technical mixtures (Schulz, 1968). The frequency of its occurrence may have been underestimated to date. Headache is a frequent symptom after exposures to technical mixtures containing TCDD.

Sensory neuropathy has been noted in many instances. Usually workers in the initial stages of exposure will complain of pains in their joints after they have very acute severe chloracne; however, there are usually no abnormal physical findings in the joints, but the complaints may continue. In early studies of workers affected by TCDD, no attempts were made to objectively measure the effects on the sensory nervous system.

Tests have now been developed that evaluate sensory nerves and that can be used in future field studies. The nerve conduction tests, which primarily have been used so far, are actually not very useful to measure neuropathy. Differences in nerve conduction were shown among residents from Seveso, Italy, who had chloracne and those who did not (Richert, von, 1962; Fillipini et al., 1981).

Sight disturbance may be related to alkaline exposure or to conjunctivitis related to effects on the glands of Meibom. Loss of hearing, taste, and smell have been reported in a few cases, but a causal relationship to TCDD exposure is doubtful. 

8.3.4 Psychiatric effects

The symptoms have been listed in Table 64 in what is believed to be their order of frequency and degree of severity.

Signs and symptoms related to accidental exposure to TCDD are given in Table 64. However, it should be observed that all the accidents and occupational contamination concern exposure to a mixture of compounds where TCDD was only one component. In all cases, its concentration in the mixtures was unknown. Only two cases of intoxication with "pure" TCDD have been reported.

The story of the discovery of TCDD is by now well documented (Holmstedt, 1980; Sandermann, 1984a,b). TCDD was synthetized in 1955. Four people were intoxicated, one co-worker severely so while drying crystals. In all cases, decreased libido was the first symptom, followed by other symptoms such as moderate to severe chloracne, sleeping difficulties, inability to concentrate, depression, and, in at least one case, swelling of the lymph nodes. In all cases, the signs and symptoms disappeared within a couple of years, with the exception of the chloracne in the most heavily exposed man.

The second occasion of exposure to what one must assume to be pure TCDD is the one reported by Oliver (1975). The toxic effects on three young scientists who suffered "transient minimal exposure to TCDD" were described. Two of them suffered from typical chloracne. Delayed symptoms about two years after initial exposure occurred in two of the scientists. These symptoms were said to have included personality changes, other neurological disturbances, and hirsutism.

All three scientists were found to have raised serum cholesterol levels, but no other biochemical disturbances and no porphyrinuria or liver damage were demonstrated. Whether the unusually delayed physiological effects were in fact due to the initial dioxin exposure is a question that was discussed by the author. Although conclusive evidence is lacking, it seems likely that these delayed effects were in fact due to dioxin intoxication. The conditions of exposure remain unexplained.

Of the many cases of exposure reported in Table 63, only two (at Monsanto in 1949 and at BASF in 1953) have been adequately followed up epidemiologically with matched control groups.

The workers of Monsanto, USA, have been investigated several times between 1949 and 1984. Immediately after the accident, Ashe & Suskind (1949) hospitalized and studied four cases of severe poisoning among the workers. These four workers were diagnosed as having chloracne, but by the time of examination these men had recovered from earlier symptoms of peripheral neuropathy. In 1950, a further examination of these four workers and two additional men revealed continued irritability, nervousness, and insomnia (Ashe & Suskind, 1950). A consistent loss of libido and some impotence was reported. Further clinical examination revealed hepatomegaly, altered prothrombin times, and disturbed lipid metabolism.

A further study of 36 workers from this plant was undertaken in 1953 (Suskind et al., 1953). It was noted that even those who developed, to a moderate or severe degree, the skin eruptions, pains in back, dyspnoea, fatigue, nervousness, and decreased libido generally improved. Even those suffering the most severe cutaneous eruptions initially had only a few or no lesions in 1953.

More recent studies on these workers are those of Zack & Suskind (1980) and Zack & Gaffey (1983). Zack and Gaffey reported on a 121-member study cohort, with a presumptive high-peak exposure to TCDD base on chloracne occurrence, which was followed for mortality until 1978. The entire cohort was traced; there were 32 deaths; 89 people were still alive. There was no excess in total mortality or in deaths from malignant neoplasms.

The proportional mortality analysis of decedents according to exposure by 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) indicated no unusual patterns of mortality. The proportional mortality ratio (PMR) for malignant neoplasms was low (PMR = 82) in the exposed group. Lung cancer was the only site among the malignant neoplasms for which the value was somewhat higher in the exposed group.

The Monsanto workers were again examined in 1984 (Suskind & Herzberg, 1984). A clinical epidemiological study was conducted to determine the long-term health effects of workplace exposures during the process of manufacturing the herbicide 2,4,5-T, including contaminants such as TCDD. The population consisted of two cohorts, 204 clearly exposed and 163 not exposed (controls). Among the exposed workers, clinical evidence of chloracne persisted in 55.7%.

None of the controls experienced chloracne development. An association was found between the persistence of chloracne and the presence and severity of actinic elastosis of the skin. There was an association between exposure and the history of ulcers of the gastrointestinal tract. Pulmonary function values among those who were exposed and who currently smoked were lower than those who were not exposed and who currently smoked. No disturbances of sexual functions were found at this time after age adjustment. The data assembled in the study indicated no evidence of increased risk for cardio-vascular disease, hepatic disease, renal damage, or central or peripheral nervous system problems.

Another selection of the population from the same plant has been examined by another group of epidemiologists (Moses et al., 1984). Since the degree of exposure was unknown to these investigators and since chloracne is generally considered a quite reliable indicator of heavy dioxin exposure, it was decided to use chloracne as a "surrogate" for exposure and to classify the study population by its presence or absence. It was recognized that those without chloracne, but with appropriate work-exposure history, might also have had TCDD exposure and were not therefore used as "unexposed controls".

Chloracne was found in 52% of 226 workers in a 1979 cross-sectional survey at the plant where 2,4,5-T had been manufactured from 1948 to 1969. Mean duration of residual chloracne was 26 years, and in 29 subjects it had been present for 30 years. A significantly increased prevalence of abnormal gamma-glutamyl transpeptidase (GGT) and higher mean GGT were found in those with chloracne compared to those without.

Although mean triglyceride values were higher in those with chloracne, the difference was not statistically significant. Neurological examination showed a statistically significant higher prevalence of abnormal sensory findings in those with chloracne. Increased prevalence of angina and reported myocardial infarction in those with chloracne was not significant when age-adjusted.

Increased prevalence of reported sexual dysfunction and decreased libido in those with chloracne, compared to those without, was statistically significant after age adjustment. No differences were found between those with and without chloracne in serum cholesterol, total urinary porphyrins, or in reproductive outcomes. Exposure to TCDD in 2,4,5-T production may thus result in apparently permanent changes in the skin.

Sensory changes in peripheral nerves and possible changes in liver metabolism in those with current or past chloracne are also suggested by these data. Based on worker histories, even severe acute toxicological effects of TCDD are reversible, or improve markedly over time. While the cross-sectional nature of this study, the low participation rate, and the highly select nature of the population limit the conclusions that can be drawn, it is unlikely that permanent, severe, and debilitating toxicological sequelae are inevitable after exposure toTCDD sufficient to produce chloracne. It must be noted, however, that individual susceptibility may make certain workers with heavy exposures more vulnerable.

The exposure of workers at BASF in 1953 has been the subject of several reviews, the latest one being that of Thiess et al. (1982). Twenty-seven years after the accident that occurred in the BASF Ludwigshafen plant, a mortality study was undertaken of people exposed in the uncontrolled reaction which occurred during the trichlorophenol process. The follow-up was 100% successful and involved 74 people. Overall mortality (21 deaths) did not differ in this group from the rate expected in three external reference populations, or from that observed in two internal comparison groups, where 18-20 deaths were observed. Of the 21 deceased people, 7 had had cancer, compared with 4.1 expected.

In addition, two other cases of cancer (one bronchial carcinoma and one carcinoma of the prostate) were still alive at the time of writing. Three deaths due to stomach cancer at ages 64, 66, and 69 years, were found, compared with 0.6 expected from regional mortality data. One stomach cancer occurred among 148 individuals in the two comparison cohorts. The incidence of cancer in these workers was considerably greater than expected and cannot be explained only as a chance event. Of 74 people, 66 had severe chloracne or severe dermatitis.

There is a possibility that some members of the BASF cohort were exposed to other unknown occupational hazards before or after the accident. However, the use of two internal comparison groups composed of matched controls from the same factory was designed to control for, as far as possible, other occupational exposures that could be important etiological or confounding factors. Because of the small size of the cohort and the small absolute number of deaths from any particular cause, the results of this study do not permit any definite conclusions concerning the carcinogenic effect of exposure.

In comparison with the above-mentioned, well conducted long-term epidemiological studies, a host of other follow-up studies have been published, none of which used adequate controls. They are, therefore, of less value but will be briefly summarized here. Jirasek et al. (1973, 1976) and Pazderova et al. (1974, 1980, 1981) examined 55 of a total of 80 workers who suffered intoxication during the manufacture of sodium pentachlorophenate and the sodium salt and butyl ester of 2,4,5-T.

One worker died from severe acute intoxication at an early stage (Jirasek et al., 1976), and 76 workers developed chloracne. The following additional symptoms were found: porphyria cutanea tarda, disorders of the metabolism of lipids, porphyrins, and carbohydrates, and alteration of plasma proteins. Hepatic lesions were also present. Neurological and electromyographic (EMG) examinations revealed peripheral nerve changes in 17 people, first detected in 8 people during the second year of the study.

A neurasthenic syndrome was also observed. The patients with porphyria cutanea tarda showed hyperpigmentation, hypertrichosis, and bullosis actinica mechanica. Porphyrin excretion in urine ranged from 172 to 2230 µg/24 h. Polyneuropathies, confirmed by EMG examination, were noted, predominantly in the lower extremities. In this outbreak, the disease was progressive during the first 2 years; subsequently the dermatological symptoms as well as the porphyric disease and the neurological disorders improved. The impaired lipid metabolism improved only very slowly.

In this plant, the toxic substances were led off through the breathing zone of the workers. The concentrations of the chlorinated hydrocarbons in the air were never measured. Due to insufficient data, the real hygienic conditions at the work place could not be accurately reconstructed. The manufacturing of 2,4,5-T was halted permanently in 1968 so that it was impossible to obtain the necessary information in an adequate manner.

From 1959 to 1964, according to information from the plant, only sodium pentachlorophenate was manufactured. Not until1965 was the manufacture of sodium 2,4,5-T commenced on a pilot scale, and later the butyl ester of 2,4,5-T was also manufactured. After each year of production, something was always changed or modified in the process and technology so that actually there was never full-scale production in the true sense of the word. Many of the herbicides manufactured could not be found from the documentation (Pazderova et al., 1974).

The uncertain mixture of compounds involved in the Spolana episode makes interpretation of signs and symptoms almost impossible. In all likelihood the porphyria observed was due to the hexachlorobenzene stated to be produced at this factory.

Signs of disturbance in the porphyrin metabolism in workers manufacturing 2,4,5-T was also described by Poland et al. (1971). Chloracne was not correlated significantly with job location within the plant, duration of employment, or coproporphyrin excretion.

Although 11 subjects with uroporphyria and at least three with overt porphyria cutanea tarda had been found in a study of the same plant six years earlier (Bleiberg et al., 1964), no clinical porphyria could be documented at the time of the second investigation, and only one worker had persistent uroporphyrinuria.

Evidence of toxicity in other organ systems was markedly less than that reported in previous studies and in most instances there was no difference from normal populations. In all likelihood the porphyria cutanea tarda in this case, as in the study from Czechoslovakia, was due to a compound other than TCDD. This is corroborated by a recent re-evaluation of the literature (Jones & Chelsky, 1986).

A study from northern Germany was published by Bauer et al. (1961). It is not clear where the cases orginated and only nine patients were studied in depth. A summary of the findings from these patients, and another person suffering from chloracne after occupational exposure to trichlorphenol, was reported by Kleu & Göltz (1971).

These patients were followed for 15 years after exposure. The severity and types of symptoms varied in a dose-related manner. Major complaints were decreased sexual activity, muscular weakness, easy fatigability, irritability, and loss of appetite and memory. The authors concluded that a permanent defect had occurred, the late form of which resembled a cerebral involutionary syndrome, combined with mental depression and neurasthenia.

A follow-up study of 11 of the 24 employees at Boehringer exhibiting skin lesions in 1955 was published by von Krause & Brassow (1978). Many continued to suffer from their earlier complaints. In seven of the eleven, nausea and intolerance to heavy fatty food was still common, and six men complained of alcohol intolerance. Although conjunctivitis had disappeared, chloracne was still clearly visible in most of the 11 subjects. Neurological problems were still severe in six of the workers.

Ten years after the incident at Coalite in 1968 when 79 workers developed chloracne due to exposure to a chlorophenol-TCDD mixture, a study was undertaken to establish the state of health of the affected employees (46) remaining in the company's employment (May, 1982). Forty-one of the 46 employees participated. The opportunity was used to examine effects on mortality, morbidity, carcinogenesis, reproduction, teratogenicity, fetotoxicity, biochemistry, immunology, and genetic changes.

Concurrently, two control groups were established, one with no dioxin exposure and the other with possible dioxin exposure. These groups were selected from within the works and matched the study group with respect to sex and age, but it was not possible to match them for occupation and social status. Half the affected subjects still had minor chloracne. Other than this finding, the authors concluded that the subjects had not been had been adversely affected in any way.

Data on the mortality of workers at the Dow Chemical company have been provided in two papers (Cook et al., 1980; Ott et al., 1980). The first of these studies describes the mortality of a cohort of 61 males involved in the preparation of trichlorophenol. Forty-nine of these workers developed chloracne, presumably as a result of skin absorption of the process contaminant TCDD.

Within the limitations posed by cohort size and length of follow-up, the exposure to chlorophenol-TCDD mixtures did not appear to have adversely affected mortality experience. Overall, four deaths occurred and 7.8 were expected. Of these, one death was due to cardiovascular disease (3.8 expected) and three deaths were attributed to cancer (1.6 expected). None of the findings was statistically significant. The second paper examined the mortality experience of 204 people exposed to 2,4,5-T during its manufacture from 1950 to 1971.

Length of employment within the 2,4,5-T process area ranged from less than one year to a maximum of approximately ten years. Efforts to minimize TCDD contamination of the product resulted in non-detectable concentrations (less than 1 mg/kg) near the end of this period. Within the scope of this mortality survey, no adverse effects were observed with respect to occupational exposure to 2,4,5-T or to its feedstock, 2,4,5-trichlorophenol.

Hardell and his co-workers in Sweden have conducted a series of case-control studies and reported an increased risk of soft-tissue sarcomas in men who were exposed to phenoxy herbicides and/or chlorophenols (Hardell & Sandsstrom, 1979; Hardell, 1981; Hardell et al., 1981; Hardell & Ericksson, 1981).

These authors also reported a case-control study that suggested that phenoxyacetic acids and chlorophenols may predispose to Hodgkin's lymphoma (Hardell et al., 1981). The relative risk was higher for a group exposed to phenoxy herbicides including 2,4,5-T and chlorophenols, i.e., pesticides that may be contaminated with PCDDs and PCDFs. However, an increased risk was still found in a group exposed mainly to phenoxy herbicides such as MCPA, 2,4-D, mecoprop and dichloroprop, i.e., pesticides with low or no contamination with PCDDs and PCDFs.

Analysis of fat levels of PCDDs and PCDFs in patients with soft tissue sarcomas and in controls failed to reveal any differences between the two groups (Nygren et al., 1986) (section 4.4.4.1).

A cohort study on Swedish farmers and gardeners has been carried out recently (Wiklund & Holm, 1986). Despite the greatly increased use of phenoxyacetic acid herbicides from 1947 to 1970, no time-related increase in the relative risk of soft-tissue sarcoma was found in the cohort or in any of the subcohorts.
The same was found by Hoar et al. (1986) although the latter study points to an increase in non-Hodgkin lymphoma. It should be noted that in all these studies the majority of the herbicides used did not contain TCDD.

In follow-up studies of workers exposed to 2,4,5-T and its precursor 2,4,5-trichlorophenol (and therefore, presumably, also to TCDD), no excessive deaths due to any cause were registered (Cook et al., 1980; Ott et al., 1980; Zack & Suskind, 1980; Zack & Gaffey, 1983). Honchar & Halperin (1981) merged the above four cohorts and found that three (2.9%) of the total 105 deaths were reported to be from soft-tissue sarcoma.

Based on national statistics only 0.07% was expected to be due to this cause. Fingerhut et al. (1984) reviewed the employment records, medical and pathological reports, tissue specimens, and death certificates for these three cases and four additional cases of deaths from soft-tissue sarcomas in these and related cohorts reported by Cook (1981), Moses & Selikoff (1981), and Johnson et al. (1981).

Three out of the seven cases had a record of chloracne and one of dermatitis. After review of the tissue specimens, five of the seven cases were diagnosed as soft-tissue sarcoma. The remaining two (which were among the three cases in the merged cohort of Honchar & Halperin (1981)) were found to be carcinoma. For three of the cases with confirmed soft-tissue sarcoma the exposure was not well documented, although an undocumented contact with 2,4,5-T, 2,4,5-trichlorophenol, or TCDD could not be excluded.

Poiger & Schlatter (1986) studied a human volunteer after ingestion of a single dose of 1.14 µg 3H-TCDD/kg body weight. The absorption from the intestine was > 87% and adipose tissue levels were 3.09 (± 0.05) and 2.85 (± 0.28) ng/kg after 13 and 69 days, respectively. The estimated half-life of TCDD was 2120 days. Gorski et al. (1984) calculated the half-lives of 1,2,3,6,7,8-hexaCDD, 1,2,3,4,6,7,8-heptaCDD and octaCDF to be about 3.5, 3.6 and 2 years, respectively.

The estimation was based on the analysis of fat tissue biopsies collected with an interval of 28 months from one 14-year-old girl who for a period of about 2-3 years had been exposed to technical pentachlorophenol. Analysis was performed by gas chromatography with electron capture detection, and the isomers were confirmed by the use of several different packed and capillary columns.