[' ', '2.', 'and', 'a', 'computer.', 'It', 'can', 'provide', 'information', 'about', 'ventilation,', 'gas', 'mixing,', 'regional', 'deposition', 'and', 'clearance,', 'airway', 'caliber,', 'and', 'relative', 'humidity.', 'A', 'bolus', 'becomes', 'more', 'and', 'more', 'dispersed', 'as', 'it', 'penetrates', 'into', 'the', 'lung.', 'The', 'deeper', 'it', 'goes,', 'the', 'more', 'particles', 'are', 'lost.', 'But', 'the', 'number', 'of', 'particies', 'lessens', 'in', 'the', 'most', 'distant', 'parts', 'of', 'the', 'dung.', 'Heyder', 'did', 'one', 'study', 'in', 'which', 'he', 'measured', 'the', 'airway', 'diameters', 'of', 'various', 'subjects,', 'including', 'some', 'who', 'were', 'smokers.', 'Their', 'diam-', 'eters', 'were', 'less', 'than', 'were', 'those', 'of', 'nonsmokers.', '15.', 'R.A.', 'GRIESEMER', 'of', 'Oak', 'Ridge', 'National', 'Laboratory', 'discused', 'the', 'problems', 'and', 'difficulties', 'in', 'doing', 'animal', 'inhalation', 'studies,', 'pointing', 'out', 'a', 'variety', 'of', 'factors', 'that', 'require', 'careful', 'assessment', 'as', 'well', 'as', 'understanding.', 'Even', 'the', 'type', 'of', 'cage', 'in', 'which', 'animals', 'are', 'held', 'may', 'affect', 'their', 'survival', 'and', 'therefore', 'the', 'results,', 'he', 'said.', ' ', 'Griesemer', 'said', 'inhalation', 'bioassays', 'really', "aren't", 'very', 'sensi-', 'tive,', 'noting', 'that', 'in', 'a', 'lifetime', 'smoke', 'exposure', 'experiment', 'in', 'his', 'laboratory,', 'only', '7', 'of', '80', 'animals', 'developed', 'lung', 'cancer.', 'The', 'inci-', 'dence', 'of', 'cancer', 'induction', 'was', 'much', 'higher', 'when', 'smoke', 'condensate', 'was', 'instilled', 'into', 'the', "animals'", 'lungs.', 'As', 'an', 'example', 'of', 'the', 'problems', 'in', 'inhalation', 'research,', 'he', 'said,', 'one', 'can', 'get', 'different', 'results', 'the', 'second', 'time', 'around', 'with', 'the', 'same', 'material', 'in', 'the', 'same', 'laboratory', 'with', 'the', 'same', 'people', 'and', 'the', 'same', 'animals.', 'We', 'just', "don't", 'know', 'why', 'this', 'happens.', 'A', 'somewhat', 'similar', 'view', 'was', 'expressed', 'by', 'P.E.', 'MORROW,', 'Univer-', 'sity', '.of', 'Rochester', '(NY),', 'who', 'said', 'long-term', 'animal', 'inhalation', 'studies', 'can', 'take', 'five', 'or', 'more', 'years', 'and', 'cost', 'aver', '$3~million.', ' ', ' ', 'He', 'cautioned', '{as', 'did', 'Mauderly', 'earlier)', 'about', 'dust', '“overload-', 'ing"', 'in', 'inhalation', 'research', 'and', 'said', "there's", 'growing', 'evidence', 'this', 'is', 'occurring', 'in', 'many', 'studies.', 'Too', 'much', 'dust', 'retained', 'by', 'the', 'animal', 'jleads', 'to', 'unknown', 'pathological', 'conditions', 'that', 'can', 'cause', '4', 'tumors.', 'Obviously,', 'the', 'tumors', 'are', 'related', 'more', 'to', 'the', 'dust', 'than', 'to', 'the', 'material', 'being', 'tested', 'for', 'toxicity.', 'He', 'said', 'overloading', 'of', 'the', 'animal', 'also', 'can', 'resuit', 'from', 'injec-', 'tion', 'or', 'ingestion', 'of', 'materials.', '16.', 'Cytotoxic,', 'mutagenic', 'and', 'carcinogenic', 'effects', 'of', 'airborne', '.', 'particulates', 'were', 'described', 'by', 'N.H.', 'SEEMAYER', 'of', 'Dusseidorf,', 'West', 'Ps', 'Germany.', 'Epidemiological', 'studies', 'show', 'a', 'higher', 'lung', 'cancer', 'incidence', 'in', 'industrialized', 'areas', 'as', 'a', 'probable', 'result', 'of', 'air', 'pollutants,', 'he', 'said.', 'There', 'are', 'more', 'than', '670', 'organic', 'chemicals', 'that', 'are', '.', 'poten-', 'tial', 'air', 'pollutants;', 'of', 'these,', '77', 'are', 'potential', 'human', 'carcino=', 'gens,', '25', 'are', 'recognized', 'as', 'human', 'carcinogens,', 'and', '20', 'are', 'suspec—', 'ted', 'human', 'carcinogens.', '620804826']