['Page', '7', 'MATERIALS', 'AND', 'METHODS', 'Experimental', 'Design', 'Female', 'rats', 'were', 'whole-body', 'exposed', 'to', 'RASS', 'at', 'concentrations', 'of', '6', 'and', '12', 'ug', 'TPM/l', '(WB6', 'and', 'WB12)', 'or', 'to', 'filtered,', 'conditioned', 'fresh', 'air', '(WBO,', 'sham-exposed', 'group)', 'for', '12', 'h', 'per', 'day,', '5', 'days', 'per', 'week,', 'for', '12', 'months', '(Table', '1).', 'For', 'the', 'comparison', 'of', 'exposure', 'modes,', 'another', 'group', 'of', 'rats', 'was', 'head-only', 'exposed', 'for', '5', 'days', 'per', 'week', 'for', '12', 'months', 'to', 'the', 'high', 'RASS', 'concentration', '(HO12),', 'but', 'only', 'for', '7', 'h', 'per', 'day,', 'which', 'is', 'considered', 'the', 'maximum', 'daily', 'exposure', 'duration', 'for', 'this', 'exposure', 'mode.', 'Due', 'to', 'laboratory', 'capacity', 'restraints,', 'the', 'inclusion', 'of', 'a', 'head-only', 'sham-exposed', 'control', 'group', 'was', 'not', 'possible.', 'However,', 'this', 'is', 'not', 'considered', 'to', 'seriously', 'impact', 'the', 'comparison', 'of', 'the', 'two', 'exposure', 'modes', 'for', 'most', 'of', 'the', 'end', 'points', 'investigated.', 'The', 'two', 'exposure', 'modes', 'were', 'compared', 'based', 'on', 'the', 'TPM', 'concentration', 'as', 'well', 'as', 'on', 'the', 'daily', 'TPM', 'dose', 'for', 'those', 'end', 'points', 'presumably', 'unaffected', 'by', 'tube', 'restraint.', 'Interim', 'investigations', 'of', 'pulmonary', 'inflammation', 'and', 'oxidative', 'DNA', 'damage,', 'end', 'points', 'not', 'previously', 'included', 'in', 'subchronic', 'SS', 'inhalation', 'studies,', 'were', 'performed', 'after', '6', 'months', 'of', 'inhalation', 'for', 'WBO', 'and', 'WB12', 'only.', 'The', 'study', 'was', 'performed', 'in', 'conformity', 'with', 'the', 'American', 'Association', 'for', 'Laboratory', 'Animal', 'Science', 'Policy', 'on', 'the', 'Humane', 'Care', 'and', 'Use', 'of', 'Laboratory', 'Animals', '(1991).', 'Experimental', 'Animals', 'Female', 'outbred', 'Wistar', 'rats', '(Cri:', '(WI)\\WU', 'BR),', 'bred', 'under', 'specified', 'pathogen-free', 'conditions,', 'were', 'obtained', 'from', 'Charles', 'River', '(Sulzfeld,', 'Germany).', 'Wistar', 'rats', 'were', 'used', 'in', 'the', 'present', 'study', 'because', 'of', 'their', 'potential', 'suitability', 'for', 'long-term', 'inhalation', 'bioassays', 'in', 'terms', 'of', 'longevity,', 'moderate', 'body', 'weight', 'development,', 'low', 'rate', 'of', 'spontaneous', 'tumors,', 'particularly', 'in', 'the', 'lungs,', 'and', 'sensitivity', 'to', 'rat', 'respiratory', 'tract', 'carcinogens', '(Woutersen', 'et', 'al.,', 'oooreggL0e', 'wae', 'T']