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versity Clinic of Thoracic and Cardiovascular Surgery, Aarhus, Denmark.

Early diagnosis of lung cancer is essential for curative surgery. In attempt to detect pre- symptomatic lung cancer, sputum cytology was chosen as screening method in order to cause as little inconvenience for the patient as possible.

The study group included 2379 cigarette smoking men aged 53-57 years. This group re- ceived by mail 5 glasses with alcohol and an instruction how to expectorate 5 consecutive mornings.

So far 1872 (79%) samples have been studied of whom 1845 were classified as "normal". In' 27 patients abnormal cells were seen, 21 with mild dysplasia, 1 with marked dysplasia and 5 with cancer cells.

Further controls have revealed lung cancer in 2 of the 21 patients with mild dysplasia. In 5 patients with cancer cells, one exfoli- ating malignant cells for 2½ years has been studied 7 times without localization of the tumor. Two patients had positive x-ray studies, and lobectomy and pneumonectomy were under- taken. Two patients with occult lung cancer died, because of cardial incompensation and distant metastases, respectively.

This study cannot support sputum cytology alone as a method to detect presymptomatic lung cancer in high risk group.

A More Refined~thod for the Estimation of "Smokers-At-Risk". Ayiomamitis, A., Badawi, I. Department of Pre- ventive Medicine and Biostatistics, Faculty of Medicine. University of Toronto, Toronto, Canada M5S IA8.

Lung cancer is the number one cause of death in Canadian males aged 35-84 (for all five-year age groups) and the second or third leading cause of death in Canadian women aged 35-74 (for all five-year age groups). It is generally believed that tobacco is the most significant and yet most easily controllable risk factor for carcinoma of the trachea, bronchus, and lung. Although many analyses have shown a strong correspondance between carcinoma of the lung and tobacco consumption, they are limited by the use of per capita con- sumption rates (which disregard the age-sex distribution of smokers). In order to assess the magnitude of this lack of accuracy, tobac- co consumption rates for Canadian (1929+) have been evaluated using four methods of computa- tion (from the simple per capita consumption rate to the age-sex standardized consumption rate) using data collected from the publica- tions of Statistics Canada for five types of tobacco (cigerettes, cigars, chewing and smo- king tobacco, snuff). Virtually identical consumption rates were obtained using the total population and the total population

aged 15 and above for estimating person-years

exposure. Rates, greater by a factor of three to four, were obtained when person-years ex- posure was derived from age-sex-specific smo- king rates and estimates the proportion of smo- kers in the population (these two rates were also virtually identical). Significant diffe- rences were also observed in the distribution of secular consumption rates obtained for each of the four estimates of "smokers-at-risk". It would appear that estimates of "smokers- at-risk" utilizing age-sex-specific smoking rates are the most suitable in analyses incor- porating tobacco consumption in their analyses.

2, EPIDEMIOLOGY AND ETIOLOGY

4-Nitroquinoline l-Oide (4NQO)-Induced Pulmo- nary Carcinogenesis in Syrian Golden Hamsters. Ito, T., Inayama, Y., Kitamura, H., Kanisawa, M. Department of Pathology, Yokohama City University School of Medicine Yokohama, Japan.

4NQO-induced pulmonary alterations were studied morphologically at the acute, subchro- nic and chronic stages using hamsters. In the acute experiment, the animals were treated with a single subcutaneous injection of 120 mg/kg body wt of 4NQO and sacrificed from 6 hr to 4 weeks after the treatment. The epi- thelial cells in the distal airway specifi- cally showed degenerative changes, but the pulmonary endocrine cells were not so injured. In the process of repairing the damaged lung tissue, type II alveolar cell hyperplasia and proliferation of immature cells around the bronchiolo-alveolar junctional area appear- ed to establish bronchiolization just around the junctional area.

In the subchronic and chronic experiments, the animals were treated with a subcutaneous injection of 20 mg/kg body wt weekly for 3 weeks, and sacrified at 20, 25 and 30 weeks (subchronic) ; and 65 and 80 weeks (chronic) after the treatment. Lung tissues were seri~ ally sectioned. In the subchronic stage, all the experimental animals examined contained pulmonary endocrine cell hyperplasia which showed argyrophilia and weakly positive im- muno-reactivity to neuron specific enolase. In the chronic stage, adenomatous lesions were included in 2 experimental animals out of 25. The pulmonary endocrine cell hyper- plasia remained but did not develop to much progressed features.

Photodegradation of Polycyclic Aromatic Hydro- carbons (PAH) in Real Conditions. Possible Effects on Lung Risk in Exposed Populations. Valerio, F., Lazzarotto, A. Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.

Though many data exist on PAH concentration in atmosphere, they may not be a good index of carcinogenic risk for exposed population. Photodegradation and reaction with 03 and

N0 x may occur in real conditions, as a grow-

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ing number of experimental results demonstra-

te, but they should not be considered a mere- ly natural detoxification mechanism since many degradation products appear to be more reactive and mutagenic than parent PAH.

Our results demonstrated that sun light intensity, 0 concentration and nature of adsorbing su~strate may induce significant modifications in the kinetic of these pheno- mena.

Implications in analytical methods and in risk assessment are discussed.

Lung Cancer and the Air Pollution. One Thou-

sand Dog S in Kawasaki C~ty, Japan I 2 Takemoto , ~., Katayama , H., Abe , Y., Kawai H., Imagawa , U. i. Department of Public Health, Saitama Medical School. 2. Department of Public Health. 3. Internal Medicine, Tokyo Medical Dental University.

Lungs of the dog are good models for study- ing the relation between air pollution and lung cancer. One thousand dogs with recorded life histories in Kawasaki city were autop- sied. As results of histopathological studies, their degrees of lung contamination increas- ed with age. 43.0% of the old dogs from the industrial area had highly contamination lungs, as opposed 20.6% of the dogs to the same age group from the residential area.

The concentration of metals in the lung was usually greater in older dogs. The lungs of dog living in industrial areas exhibited significantly greater concentration of Cr, Ni, Cd, Pb, and Co, than those living in commertial and residential areas.

There were seven malignant cases included 4 from the industrial area, 1 from commertial area, 2 from the r-sidential area (lung cancer).

Therefore, air pollution is recognized to give a strong influence on the incidence on lung contamination and lung cancer of dogs.

Rat Lung Carcinoma Produced by 2 Year Inhala- tion of Diesel Exhaust Particulates. lwai, K., Yamagishi, M., Udagawa, T. Research Institute of Tuberculosis, Japan Anti-Tuber- culosis Association, Kiyose-shi, Tokyo 204, Japan.

Various kinds of arylhydrocarbon including dinitropyren have been detected in diesel ex- haust particulates. In vitro studies using Ames test, chromosomal aberration, sister chromatid exchange or cell transformation have revealed mutagenicity of the particulates, while evidence has been lacking under in vivo carcinogenicity until now.

Chronic inhalation studies were carried out using SPF rats of Fisher 344 strain feed- ed in aseptic chambers (Particulate 4.9 1.6 mg/m ). Diesel exhaust diluted i0 times by clean air was introduced into the animal chambers, 8 hrs/day, 7 days/week, for up to 2 years. Similarly diluted but particulate-

excluded gas or clean air was conducted to

the control chambers. Hyperplastic and metaplastic changes of

bronchiolar and type II alveolar epitheliums

were noted with increasing extent according to exposure duration, accompanying marked parti- culate deposition in alveoli. Some of them transformed into neoplastic change and to ma- lignant ones in 2 years exposed rats. Two ty- pes of malignant tumor, adenocarcinoma and adenosquamous carcinoma were seen, showing different cell character under electron-micro- scopy. Incidence of tumor (both benign and malignant) in particulated gas exposed rats (8/19 42.1%) was significantly higher than that in de-particulated (0/16 0%) or clean air (1/22 4.5%) group.

Diesel exhaust particulates have carcino- genicity in rat lung, at least in this expe- rimental model.

Lung Cancer Screening in Mining & Related In- dustries in B.C. Embree, V., Enarson, D.A., LeRiche, J., Nelems, B. Department of Medicine, Vancouver General Hospital, U.B.C., Vancouver, B.C.

3 yrs. of a 5 yr. program of lung cancer screening are completed. Sixteen sites are en- rolled: 2999 people determined eligible (40+ yrs) and available (still actively employed at time of visit). 82% (2467) are enrolled. Participants 50+ yrs. plus smoking 20+ ciga- rettes/day are followed 6-monthly with sputum sample, respiratory questionnaire and annual chest x-ray. Participation at follow-up visits is over 70% overall. Community and postal fol- low-up supplement mine site visits. Sputum samples adequate for analysis have been ob- tained on 59% of participants. Overall rates of metaplasia and dysplasia are higher at sites with exposures to known carcinogens. Prevalence of metaplasia in exposed populati- on (n=599) is 3.9% vs. 1.7% in unexposed; pre- valence of dysplasia is 6.2% in exposed vs. 2% in unexposed. The occupational exposure effect masks the expected dose-response relationship of smoking on sputum results. For all sites combined, prevalence of metaplasia is 5.8%, 5.4% and 8.9% for non-smokers, <20 cig./day and 20+ cig./day respectively; prevalence of dysplasia is 3.4%, 3.2% and 5.6% respective- ly. When sites with a known occupational hazard for lung cancer are excluded, the expected dose-response relationship is apparent: pre- valence of metaplasia is 2.9%, 5.8% and 8.4% for the respective groups; prevalence of dys- plasia is 1.9%, 3.2% and 4.5% respectively.

Bronchogenic Carcinoma in Libyan Patients. A Fifteen Year Study. Wassef, S.A. The Pathology Department, Tripoli Central Hospital, Tripoli, The Socialist Peop- le's Libyan Arab Jamahiryah.

There is no reliable population-based data with regards bronchogenic carcinoma in the

Eastern Mediterranean countries and the mor-