In California, an increase in exposure by 0.01 parts per billion (ppb) to the pesticide 1,3-dichloropropene (1,3-D) resulted in a significantly greater risk for visiting the emergency department (ED) for asthma exacerbations, according to study results published in the Journal of Asthma.

Because 1,3-D is a commonly used soil fumigant, there are concerns regarding its potentially harmful impact on human beings, particularly once it becomes an ambient air toxicant after volatizing into the atmosphere surrounding farmlands. While it has been implicated in respiratory disease previously, this was the first study to explore the effect of 1,3-D exposure on asthma-based ED visits. Investigators hypothesized that short-term exposure would be associated with an increase in ED visits in central and southern California.

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A bidirectional-symmetric case-crossover study examined California state records for the period from 2005 to 2011 (1064 days), identifying asthma ED visits (n=3,878; 54% women). Conditional logistic regression analyses were used to calculate adjusted odds ratios (aORs) and 95% CIs for associations between asthma visits and a 0.01 ppb increase in 1,3-D exposure from October through February of each year. Exposure (to 1,3-D, NO2 and PM2.5, across 69 zip codes) on the day of the ED visit (event day) was compared with 4 control days — 2 before and 2 after the event day — assessed 1 day every 2 weeks. Stratification by age, sex and race/ethnicity was utilized to investigate potential effect modifications.

In all cases analyzed, a 0.01 ppb 1,3-D exposure increase on the event day was associated with a 13.5% greater risk of presenting to the ED for asthma management (aOR 1.135; 95% CI, 1.123-1.149). Upon racial stratification, 1,3-D exposure and asthma ED visits were significantly positively associated in non-Hispanic black (aOR 1.095; 95% CI, 1.035-1.155) and Hispanic (aOR 1.121; 95% CI, 1.064-1.179) individuals — representing risk increases of 9.5% and 12.1%, respectively — but not in non-Hispanic white participants (aOR 1.003; 95% CI, 0.921-1.079). Regarding age, there were significant positive associations found between exposure and ED visits in patients age 2 to 5 years (aOR 1.065; 95% CI, 1.020-1.133), 6 to 18 years (aOR 1.142; 95% CI, 1.086-1.196) and 19 to 40 years (aOR 1.023; 95% CI, 1.015-1.073), representing odds increases of 6.5%, 14.2%, and 4.4%, respectively. Associations according to sex were similar, with 8.1% (aOR 1.081; 95% CI, 1.042-1.123) and 6.9% (aOR 1.069; 95% CI, 1.035-1.103) increases in ED visit risk in men and women, respectively, following a 0.01 ppb exposure elevation.

Study strengths included limiting invariant subject confounder effects and accounting for possible confounding by other air pollutants via inclusion of NO2 and PM2.5 during regression analyses. Study limitations included potential exposure misclassification, as well as possible misclassification of asthma cases as a result of using only 1 diagnostic code.

“Considering 1,3-D as an air toxicant and preventing future exposure can help prevent life-threatening health outcomes, including severe asthmatic exacerbations,” noted the investigators. They recommended that future research explore the toxicity and pathophysiologic mechanisms of inhaled 1,3-D, and encouraged enhanced monitoring of air concentrations.

Disclosures

The authors declare that they have no conflict of interest. No funding information was provided.

Reference

Gharibi H, Entwistle MR, Schweizer D, Tavallali P, Cisneros R. The association between 1,3-dichloropropene and asthma emergency department visits in California, USA from 2005 to 2011: a bidirectional-symmetric case crossover study [published online April 2, 2019]. J Asthma. doi:10.1080/02770903.2019.1590596