symptoms in a group of 25 workers with humidifier fever and 90 workmate controls.
In general, published estimates are only educated guesses. The U.S. Environmental Protection Agency (EPA, 1991b) states that epidemics in the workplace are rare but that when they do occur, ''attack rates are high (30–75 percent)." Based on symptoms, Finnegan and coworkers (1984) estimated a rate of occurrence of 2–3 percent in Great Britain in office buildings with mechanical ventilation. Prevalence rates in the home, however, have not been evaluated (EPA, 1991b).
There are several syndromes in which a role for indoor allergens is possible or suspected but largely undefined. These include chronic sinusitis and bronchitis, sick building syndrome and other nonspecific syndromes, and acute respiratory illnesses.
Sinusitis is defined as inflammation of the sinuses, which are four pairs of hollow structures that surround the nasal cavity. Chronic sinusitis is defined by physicians as persistent inflammation of the mucosa of the sinuses lasting for more than 3 months (Slavin, 1989). Symptoms may include facial pressure, nasal stuffiness, hyposmia, prurulent nasal secretions, sore throat, fetid breath, and malaise. Coughing and wheezing occasionally occur.
Sinusitis is an important cause of morbidity (Slavin, 1989). In 1981, statistics from the U.S. Department of Health and Human Services indicated that 31 million people had chronic sinusitis; data from the National Center for Health Statistics (NCHS, 1986) are similar (13.9 percent, more than 30 million people). Sinusitis is thus more prevalent than arthritis (27 million) and hypertension (25.5 million). In Great Britain, the Department of Health and Social Security estimates that a half million working days are lost in that country each year due to sinusitis (Slavin, 1989).
In 1975, the rate of physician-confirmed sinusitis in Tucson adults was reported to be 29.4 percent (Lebowitz et al., 1975). The difference between this rate and the figures listed above does not reflect decreasing prevalence over time but rather variable case definitions.