Researchers of a study recently published in the Journal of Asthma have reported a positive association between methyl-bromide concentrations and asthma-related emergency department (ED) visits among youths between the ages of 6 and 18 years in California. This association was stronger among Hispanics and blacks than among nonHispanic whites. 

This study included 4262 visits to the ED. The study population was 44.4% Hispanic, 23.5% nonHispanic black, and 32% nonHispanic white, with 12.7% of participants aged 2 to 5 years, 24.6% aged 6 to 18 years, 30.5% aged 19 to 40 years, 25.1% aged 41 to 64 years, and 7.1% age ≥65 years (mean age 31.3±21.2). All visits took place between 2005 and 2011 in southern and central California, with data collected between August and February of each calendar year because these months contained the highest ambient air concentrations of methyl-bromide. Information was sourced from the state’s Office of Statewide Health Planning and Development. Odds ratios (ORs) with 95% CI for each 0.01-ppb increase in methyl-bromide concentration were calculated using conditional logistic regression. 

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After adjusting for the presence of other pollutants, humidity, and meteorological conditions, each 0.01-ppb increase in methyl-bromide concentration was associated with a 7.1% (95% CI, 2.9%-10.8%) greater likelihood of an asthma-related ED visit. An association was identified between higher concentrations of methyl-bromide and increased asthma-related ED visits for Hispanics (OR 1.107; 95% CI, 1.043-1.173) and nonHispanic blacks (OR 1.065; 95% CI, 1.019-1.108). This association was not present among nonHispanic whites, and among Hispanics and nonHispanic blacks, only participants between the ages of 6 and 18 years showed the association (OR 1.071; 95% CI, 1.016-1.125). 

Limitations of this study included the lack of a multipollutant model and potential exposure misclassification.

“[A]n increase in [methyl-bromide] ambient air concentration increased the odds of having an asthma ED visit in central and southern California from August to February (2005-2011),” the study researchers concluded. “Limited study on the respiratory effects of [methyl-bromide] and lack of ambient air monitoring data makes it difficult to understand the impact to public health. Without further more comprehensive studies, [methyl-bromide] should be assumed to have an impact on ED visits for asthma at current ambient concentrations.”

Reference

Gharibi H, Entwistle MR, Schweizer D, Tavallali P, Thao C, Cisneros R. Methyl-bromide and asthma emergency department visits in California, USA from 2005 to 2011 [published online July 16, 2019]. J Asthma. 2019:1-10.