Diagnostic information: Acid anhydrides are strong respiratory irritants known to produce hypersensitivity pulmonary disease, often beginning as hypersensitivity pneumonitis. Hypersensitivity pneumonitis can be precipitated either by acute or chronic exposure to acid anhydrides. Acute hypersensitivity pneumonitis may be characterized by fever, chills, nonproductive cough, chest pains, and dyspnea. Symptoms associated with chronic hypersensitivity include fever, cough, fatigue, weight loss, and shortness of breath.¹

Clinical significance: Between 2% and 15% of all asthma associated with industry is due to occupational exposure to chemicals.¹ Quantitative allergen-specific IgE testing offers the capability of monitoring workplace exposure to acid anhydrides through the measurement of acid anhydride-specific IgE levels. Increases in acid anhydride-specific IgE levels are correlated with elevations in exposure to acid anhydrides.

Sources of exposure: Phthalic anhydride (PA) and trimellitic anhydride (TMA) are two of the most widely used acid anhydrides in industry. Inhalation and dermal contact are the two most common routes of exposure to acid anhydrides in the workplace.² Acid anhydrides are used as hardeners or plasticizers in the production of many epoxy resin systems.² Acid anhydrides are also employed in some chemical and dye production processes.²