A high proportion of asthmatic subjects report that their respiratory symptoms do grow worse at work although these subjects do not actually suffer from occupational asthma with or without a latency period (see above). The presence of asthma predated the start of their jobs. Not only do these subjects report having more symptoms at work, but their also use their bronchodilators more often for relief, their bronchial calibre readings are less satisfactory, and their sputum is found to contain more «neutrophiles» (a kind of white globules). We do not know the causes and mechanisms of this deterioration of asthma, nor do we know what long-term consequences it may have on the progress of the asthmatic condition.