Published online: May 27, 2019
Asthma affects 8.3% of the U.S. population. Two heavy metals, cadmium and lead, are common environmental and occupational pollutants that may cause or worsen asthma. The general population can be exposed to cadmium or lead via contaminated water, soil, or food, while workers can be exposed by inhalation and ingestion of industrial fumes or mining dusts. Cadmium is also a major toxicant in tobacco smoke, and thus the general population and workers can be exposed to cadmium through active or passive smoking.
In a study published in this issue of The Journal of Allergy and Clinical Immunology: In Practice, Yang and colleagues examined serum cadmium or lead, current wheeze, current asthma, and lung function among 13,888 participants in the 2007-2012 National Health and Nutrition Examination Survey. The researchers found that an increased serum cadmium was associated with current wheeze and asthma in active smokers but not in never/former smokers, while serum lead was not associated with current wheeze or asthma, regardless of smoking status. Serum cadmium was associated with lower lung function measures (FEV1 and FEV1/FVC) in never/former smokers and in current smokers, but this association was stronger in never/former smokers. Moreover, serum cadmium was associated with reduced fractional exhaled nitric oxide in never/former smokers, and serum lead was associated with lower FEV1/FVC, with similar findings in never/former smokers and current smokers.
In summary, this study of U.S. adults shows that a high serum cadmium is associated with wheeze and asthma in current smokers. This may be explained by unaccounted long-term effects of smoking, joint effects of serum cadmium and current smoking, or misdiagnosis of respiratory disorders such as chronic obstructive pulmonary disease (COPD) as wheeze or asthma in current smokers. Findings from this study also suggest that exposure to higher levels of heavy metals (particularly cadmium) may negatively affect lung function in non-smokers.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.