144 TUBERCLE

theless, of 26 patients who died, only 4 showed active tuberculosis at necropsy; of 83 live patients. only 3 showedevidence of active tuberculosis when last examined. It appears that, while the incidence of pulmonary tuberculosisis abnormally high, the response to treatment is not adversly affectedby the pneurnoconiosis-e-contraryto the opinionheld by some. It may therefore no longer be necessary to advise suspension from the industry for all patients whodevelop tuberculosis.

Dr. A. Munn (Imperial Chemical Industries) discussed the 'Respiratory Hazards From Diisocyanates',which are extensively used in a variety of industries. Chemically the term implies the presence of an -NCOradicle, the intense reactivity of which is responsible for the diversity of uses for these cornpoundsand probablyfor the health hazard.

Toluene di-isocyanate (TDI) is the most important compound medically and industrially. Traditional animalexperiments showed low toxicity. Nevertheless industrial development soon produced a very real problem­respiratory symptoms in many workmen. The vapour is irritant to the respiratory tract, but only in concentrationsmuch higher than are likely to occur in industrial conditions. Symptoms are related to degree of exposure. Theysubside on removal from contact, but often recur on further exposure even to minute concentration of TDI-necessitating permanent removal. The evidence suggests sensitization, although this has not been directlyestablished. Symptoms usually appear within a few weeks of starting work with TDI; they are rare where conditionsare good, but up to 25% of workmen may be affected sooner or later if conditions are bad (and it requires greatcare to ensure that they are not bad). The MAC now recommended is 0·02 p.p.m. Permanent damage is rare andprobably results from repeated exposure after sensitization.

Diphenylmethane di-isocyanate (MDI) is of low volatility. The same MAC is recommended, but is much moreeasily attained. Protection is required for spraying operations. Sensitization is rare, in contrast to TDI-only a fewcases have been recorded.

High molecular weight di-isocyanates can be produced and are widely used. In themselves they appear to beharmless, but trouble can arise from the presence of simple di-isocyanates as impurities or as breakdown productsduring use.

Dr. R. Morley (H.M. Inspector of Factories) discussed the 'Effect of Nitrous Fumes on the Lungs',These irritate the bronchial mucosa, but unlike chlorine or ammonia, initial irritation is slight and serious effectsappear later.

In the shipyards and engineering works of the North-East, arc welding and oxy-acetylenecutting are the mostlikely causes, and in fact large amounts of nitrous fumes must be produced regularly in the operations. Nevertheless,reported cases of gassing are only 2 or 3 in a year.

There are 8 oxides of nitrogen, some of which are unstable. The actual composition of nitrous fumes is rarelyknown and it has not been possible to determine the individual toxicity of the various oxides. Ozone, which is alsoa respiratory irritant, is often produced at the same time.

Clinically cases can be classified into three types:-(l) heavy exposure causing almost immediate death; (2) caseswith delayed symptoms-pulmonary oedema developing within 48 hours, going on to death or recoveryin a few days;(3) apparent recovery from early effects of exposure, followed by severe pneumonia or bronchiolitis obliterans 2or 3 weeks later-often fatal.

Dr. N. S. Faulds (Carlisle) discussed 'Carcinoma of the Lung in Haematite Miners'. Iron ore hasbeen mined in Cumberland since Roman times. In 1913 dry drilling was introduced and there was considerableincrease in the amount of dust produced. Wet drilling and other measures have since 1923 reduced dust particlesfrom 5 million to about 2,000 per cc,

In 91 necropsies on iron-ore miners from 1932 to 1948 there were only 4 %bronchial carcinomas. During the next7 years there were 12 %and among 69 necropsies in 1963-64 there were 17%. In the entire series of 475 the incidencewas 14%, compared with 3 % of 4,253 necropsies on men over 30 years of age from all other occupations.

INTERNATIONAL UNION AGAINST TUBERCULOSIS

ANNUAL MEETING IN ABIDJANThe annual meeting will ne held in Abidjan, Ivory Coast, from August 31st to September 4th, 1966. The

administrative meetings will be on August 31st and September Ist. On September 2nd there will be a scientificmeetingon the theme of 'The Toll of Tuberculosis in Africa'. On September 3rd and 4th visits will be arranged to Lakotuand Bouake and to village treatment centres. Accommodation will be arranged at the Hotel Ivoire in Abidjan.

Further particulars can be obtained from the Secretariat of the Union, 15 Rue Pomereu, Paris 16e. Applicationfor accommodation must be made through the Secretariat by May lst,