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The present report shows that the province of Torino, Italy, (6830 sq Km, population in 1966, 2.074.893) is a high risk area for laryngeal cancer. A total of 875 cases occurring in residents in the province were forwarded to the Cancer Registry of Piedmont (RTP) in 1965–69. A histological report was available in 67.9 % cases, while in 21.8 % the death certificate was the only document with diagnosis of laryngeal cancer (table 1). Cases were uniformly distributed throughout the 5 years covered by the study: the number of cases with death certificate only progressively decreased from 59 in 1965 to 21 in 1969 (table 3). For the purposes of the present study, the province of Torino has been divided into 3 areas, i.e. the city of Torino (population 1.107.919), the 23 suburbs (total population 340.951) and the non-metropolitan part of the province (population 626.023). Among the three areas, the relative frequency of laryngeal cancer/all malignant tumours recorded at the RTP in men was 5.78 % in the city of Torino, 6.43 % in the suburbs and 4.77 % in the non-metropolitan part of the province (table 4). The difference between the city of Torino and the suburbs was not significant (p > 0.05) while the difference both between the city of Torino and the non metropolitan part of the province and between the suburbs and the non metropolitan areas was significant (p < 0.05 and p ∼ 0.01 respectively). In other cancer registries (3) the relative frequencies of laryngeal cancer were under 2.86 % with the exception of Israel (3.24 %) and Bombay (9.26 %). In women, the relative frequency of laryngeal cancer fluctuated between 0.25 and 0.32 % in the different areas of the province of Torino, i.e. in the same order of those observed in other cancer registries with the exception of Bombay (2.07%) (3). In the province of Torino considered as a whole, age standardized annual incidence/100.000 of laryngeal cancer was 12.6 in men and 0.6 in women. Incidences truncated to ages 35–64 were 25.5 and 0.9 respectively (table 5). In men these rates are approximately 5–7 times higher than those recorded in Norway, Sweden and Denmark and about 3.5–6 times higher than those recorded in the six cancer registries operating in Great Britain. A comparison between the province of Torino and other cancer registries on age specific incidences (table 6, text-fig. 3) shows that the ratio province of Torino/other registries is relatively higher at age 35–44 than later in life. This is considered as evidence of an increase of the environmental carcinogenic load in the province of Torino during recent years. In men, age standardized incidences and incidences truncated to ages 35–64 were slightly but not significantly higher in the city of Torino than in the suburbs. On the other hand, in both the city of Torino and the suburbs they were 1.5–1.7 times higher than in the non-metropolitan part of the province (table 5). The difference concerned mainly age groups over 55 (text-fig. 2). However, the incidence of laryngeal cancer truncated to ages 35–64 in the non-metropolitan part of the province of Torino was still 7.2 times higher than in the rural population of Norway and 2.1–4.1 times higher than in the six cancer registries operating in Great Britain (3). This suggests that factors connected with life in the metropolitan area of Torino (such as air pollution) are a minor cause of the excess of laryngeal cancer in the province of Torino.

Age-standardized incidence rates of cancer of the larynx in men from 1965–1969 were 14.7/100,000/year in the city of Torino and 8.4 in the non-metropolitan area of the province. These rates are among the highest in Europe. The geographical distribution of cancer of the larynx has been investigated in the non-metropolitan area considering two geographical entities, i.e., the 291 towns and the 12 ecological zones/subzones of the area. The incidence of cancer of the larynx in men was unrelated to the population of towns in 1961, whereas it was positively correlated to indexes of general industrialization as well as to those related to industrialization in the mechanical processes. Tobacco and alcohol consumption have not been taken into account. In order to validate the methodology, the investigation was extended to bladder cancer and to cancer in children. The former was correlated with general and chemical + rubber industrialization, whereas the latter was not correlated with any industrial process.