Occupational exposure to formaldehyde often causes nasal discomfort. The objective of this study was to determine whether chronic exposure to formaldehyde causes annoying symptoms by direct irritation and whether it affects all exposed people (through hyperreactivity in atopic persons, through formaldehyde-induced hyperreactivity also in nonatopic persons, or through an immunologically mediated, immediate type 1 reaction to formaldehyde itself). It was found that about 50% of the studied population of 66 workers occupationally exposed to formaldehyde during formaldehyde production experienced nasal discomfort through hyperreactivity. Atopics were not significantly overrepresented among the persons with occupational nasal symptoms. Two workers with isolated occupational nasal discomfort, and sensitized by long-term inhalation, had a positive radioallergosorbent test for formaldehyde. The conclusion was reached that exposure to formaldehyde should be minimized as much as possible for all people, not only for atopic persons.

Medium-density fiber (MDF) board was recently introduced in the furniture industry. In this pilot study health complaints, physiology, and histology of the upper airways were evaluated for two groups of workers, one handling MDF board for at least one-third of their work week (MDF group) and another handling traditional fiber board. Civil servants served as a reference group. The frequency of health complaints concerning the airways was higher, the sense of smell was poorer, and the frequency of nasal obstruction measured with rhinomanometry was higher for the MDF group, while mucociliary activity was lower in the group handling traditional board. In both groups forced vital capacity was low when compared with expected values. Histological specimens from the middle turbinate of the nose showed, in a few cases, nasal epithelial dysplasia in the traditional board group, but histological changes in terms of scoring did not differ significantly between the groups.

To investigate health effects of long-term exposure to formaldehyde a cross-sectional field study was performed. Seventy formaldehyde-exposed workers were compared with a control group. A higher frequency of symptoms from upper and lower airways, headache, and dermal discomfort was found in the formaldehyde-exposed group. Further, formaldehyde-exposed workers showed disturbances of nasal physiologic conditions, such as slow nasal clearance, impairment of the sense of smell, more pronounced nasal mucosal swelling, and by spirometry lower forced vital capacity than expected was found. Nasal biopsies from the concha media showed more frequent histologic changes such as loss of cilia and metaplasia in the formaldehyde-exposed group. Histologic lesions did not correlate to current or cumulative exposure doses to formaldehyde. In an experimental study of Sprague-Dawley rats exposed to formaldehyde (12.7 mg/m3, 6 hours/day, 5 days/week for 24 months), one rat developed a squamous cell carcinoma in the nose and another nasal dysplasia and in seven other rats pronounced nasal metaplasia was seen in the nasal mucosa. In a control group of rats no significant histologic lesions were found.

In the nasal mucosa of rodents, both formaldehyde and wood dust have proved to be carcinogenic. Wood dust is also a well-known nasal carcinogen in man. The effects of long-term exposure of humans to formaldehyde, however, are more obscure. In this investigation two groups of workers with well-defined exposure to formaldehyde and to formaldehyde and wood dust, respectively, were compared with a control group regarding histological changes in nasal specimens from the middle turbinate. Significant changes were found in the formaldehyde group but not in the group exposed to both formaldehyde and wood dust. No correlation was found between histological changes and duration of exposure, doses of exposure or smoking habits.

Wood dust is a well known nasal carcinogen in man, as formaldehyde is in rats. In certain occupational environments, combined exposure to wood dust and formaldehyde is common. Little is known about the effects of this combination. A pilot study was performed on four groups of Sprague-Dawley rats: one exposed to wood dust (25 mg/m3), another to formaldehyde (12.4 ppm) and a third to both wood dust and formaldehyde; the fourth group served a control group. After 104 weeks of exposure the nose and lungs were examined histologically. One well differentiated squamous cell carcinoma was found in the formaldehyde group. Squamous cell metaplasia was found significantly more often among the formaldehyde-exposed rats. Squamous cell metaplasia with dysplasia was most frequently observed, however, in the group exposed to both formaldehyde and wood dust. There were also significantly more rats with pulmonary emphysema in the groups exposed to wood dust than in the other groups.

Sprague-Dawley rats were vaccinated with pneumococcal polysaccharide antigens and tetanus toxoid to evaluate the immunologic effects of long-term formaldehyde exposure. The antibody response to vaccination was measured 3 to 4 weeks later by enzyme-linked immunosorbent assay. An IgG response to pneumococcal polysaccharides and to tetanus toxoid was found in both the formaldehyde-exposed group and a control group of rats not exposed to formaldehyde. The IgM response to tetanus toxoid was significant in both groups but neither group showed a significant IgM response to pneumococcal polysaccharides. There were thus no signs of impaired B-cell function in rats exposed to a high concentration (12.6 ppm) of formaldehyde for nearly 2 years.

The hazards of exposure to formaldehyde have been widely discussed in recent years on account of the health complaints of exposed persons. Both domestic and occupational exposure to formaldehyde is common. In the present study the effects of formaldehyde alone and in combination with wood dust, another nasal irritant, on the upper and lower respiratory tract have been investigated. The effects were correlated with the duration and degree of exposure. Discomfort from both the upper and lower airways was more frequent in the exposed group than in the unexposed group. Nasal obstruction among the exposed subjects in general could not be detected by rhinomanometric measurements, but, for the group exposed to formaldehyde alone and with a history of nasal blocking, there was significant nasal mucosal swelling. The nasal mucociliary clearance was significantly delayed, and the sense of smell was significantly reduced in the exposed groups when they were compared with the referents. Spirometry showed a significantly decreased forced vital capacity in the exposed groups. There were no signs in this investigation that duration of exposure or level of exposure to formaldehyde would have any influence on the severity of symptoms or the impairment of physiological conditions.

The histological study of the non-tumours nasal mucosa in 22 wood-workers with ethmoidal adenocarcinoma was carried out and special attention was paid to the presence of cuboidal metaplasia with or without dysplasia. The workers had been exposed to wood dust for an average of 38 years (range 18 to 55 years). In 19 cases cuboidal metaplasia was found and 16 of these also had dysplasia. In 10 cases there was a transitional zone with dysplastic cuboidal epithelium in continuity with the tumour. In 5 cases there was squamous metaplasia. The results indicate cuboidal metaplasia with dysplasia being a possible precursor to nasal adenocarcinoma in workers exposed to wood dust, similar to the findings of squamous metaplasia and squamous cell carcinoma in nickel workers.

Fine wood dust is epidemiologically associated with human nasal cancer. The aim of the present study was to elaborate an animal model for inhalation studies of the effects of fine wood dust on the upper and lower airways. Syrian golden hamsters were used. After 10 months one animal in the group which was exposed only to wood dust, had developed a malignant nasal tumour and another animal in the same group had nasal dysplasia. Spontaneous nasal tumours in this laboratory animal is not known. Many tumours of the nose, larynx and trachea arose in animals treated with a carcinogen (diethylnitrosamine). There was no increase in tumours in animals with combined exposure to diethylnitrosamine and wood dust.

Of 24 Syrian golden hamsters exposed to wood dust in a concentration in the air of 30 mg/m3 for 6 h per day, 5 days a week, for a period of 40 weeks, one animal got dysplasia and one a malignant tumour in the nasal mucosa. In a group of 24 animals given 3 mg of diethylnitrosamine subcutaneously once a week for 12 weeks, a high frequency of benign and malignant tumours (mainly adenocarcinoma) of the nasal mucosa was found, but a group of similar size exposed to both wood dust and diethylnitrosamine did not show a higher frequency of nasal tumours than those given this latter substance alone.

The incidence of nasal adenocarcinoma is greatly increased in wood dust exposed furniture workers. The background is discussed and histological and cytological examinations are performed in 45 workers. The histological findings are compared with different kinds of cytological methods, May-Grünwald-Giemsa and Papanicolau. It was a significant increase in cuboidal cell metaplasia revealed by histology and Papanicolau stained cytology. MGG, on the other hand, revealed significantly raised occurrence of goblet cell hyperplasia. These findings are discussed in relation to a morphogenetical model which could explain some features in the development of premalignant changes which could precede nasal adenocarcinomas.

The occurrence of symptoms from the upper airways in the furniture industry was studied by means of a questionnaire which was answered by 676 wood furniture workers from 50 different factories. Twenty per cent reported nasal hypersecretion and 40% nasal obstruction. A randomized sample of 61 workers was investigated further. Rhinomanometry confirmed the sense of nasal obstruction objectively. The air-conditioning capacity was normal. Nasal clearance was reduced in 54% of the wood-workers. Spirometry revealed a significantly reduced forced expiratory vital capacity in the investigated workers, compared with a normal reference material. The mean concentration of wood dust was 2.0 mg/m3 air (range 0.30-5.06 mg/m3). These results have initiated further allergological and morphological studies in wood furniture workers.

Occupational nasal allergies were studied in six wood furniture factories. The concentration of moulds, wood dust and endotoxins was registered and occasionally high values were found. Paecilomyces spec. was the most common mould. A special questionnaire showed that 16% (42/268) of the wood workers with a mean exposure time of 12 years had a history compatible with hypersensitivity in the upper airways associated to their work. Rhinomanometric investigations showed mucosal congestion in the workers with nasal discomfort and nasal clearance was pathologically slow in 54%. Histological studies revealed a high incidence of unciliated and metaplastic nasal epithelium. Skin prick tests and provocation tests with standard allergens and allergens prepared from the moulds and the wood dust in the environment showed that the wood furniture workers had an incidence of allergy to moulds in 3% and to wood dust in 2%. Most of the workers sensitive to moulds and/or woods were also skin prick sensitive to other allergens. No statistical difference concerning the presence of precipitating antibodies against mould and wood antigens could be registered between workers with discomfort and workers without symptoms.