Sulfur Used as Pesticide Linked to Lung Problems in Children

Nicola M. Parry, DVM

August 16, 2017

Use of elemental sulfur, a commonly used pesticide, may adversely affect the respiratory health of children living near fields in which the pesticide is applied, a new study shows.

Rachel Raanan, PhD, from the University of California, Berkeley, and colleagues published the results of their longitudinal birth cohort study online August 14 in Environmental Health Perspectives.

"We now present the first report of an association between poorer respiratory health and nearby agricultural use of elemental sulfur — one of the most heavily used agricultural pesticides," the authors write. "Specifically, we found poorer lung function (FEV1 [forced expiratory volume in 1 second], FVC [forced vital capacity], and [forced expiratory flow 25%-75%]) and higher odds of reported respiratory symptoms and asthma medication use assessed at 7 [years] of age in children living within 0.5 km and 1 km of elemental sulfur applications during the previous week, month, and year. These findings were independent of exposure to [organophosphate pesticides]."

Elemental sulfur is the most widely used pesticide in California and Europe. Although the US Environmental Protection Agency recognizes it as safe for human health, studies have reported that elemental sulfur causes ocular symptoms, dermatitis, and respiratory or systemic illness in exposed farmworkers.

Elemental sulfur has also been shown to induce contact dermatitis or breathing difficulties in animal studies, depending on its route of administration.

However, the health effects of elemental sulfur on people living near treated fields had not previously been investigated, despite its widespread agricultural use and the potential for drift after application.

Dr Raanan and colleagues therefore examined possible associations between lung function and respiratory symptoms in children living in an agricultural community near sulfur-treated fields.

The children included in the study were enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a longitudinal birth cohort study evaluating environmental exposures in children living in the Salinas Valley, California.

The researchers questioned mothers about children's respiratory symptoms and medication use, collecting information for 347 children at 7 years of age. In addition, 279 children underwent lung function tests.

Estimations of proximity to sulfur-treated fields and relevant covariate data were available for 237 children for whom the researchers had symptomatology information, and 205 for whom they had FEV1 measurements.

The authors included proximity to agricultural fields as a covariate in sensitivity analyses because they wanted to control for other potential factors, such as other pesticides, in the fields. "We have previously reported that exposure to organophosphate pesticides...as measured by dialkyl phosphate metabolites in the urine of the children was adversely associated with respiratory health in this population of children living in the Salinas Valley, California," they explain.

According to the authors, of the 237 children for whom information on both respiratory symptoms and proximity to sulfur-treated fields was available, 89.0% were born to immigrant families, and 63.4% were living with at least one agricultural worker in the home.

The researchers found that children living within 0.5 and 1 km of fields treated with elemental sulfur during the year before pulmonary evaluation had poorer lung function and higher odds of reported respiratory symptoms and asthma medication use.

In particular, a 10-fold increase in the estimated amount of sulfur applied within 1 km of a child's home during the previous year was associated with a 3.5-fold increased odds of asthma medication usage (odds ratio [OR], 3.51; 95% confidence interval [CI], 1.50 - 8.23; P = .004) and a twofold increased risk of having respiratory symptoms such as wheezing and shortness of breath (OR, 2.09; 95% CI, 1.27 - 3.46; P = .004).

The researchers also found that each 10-fold increase in the amount of sulfur applied during the previous year within a 1-km radius of the home was associated with an average FEV1 decrease of 143 milliliters/second (95% CI, −0.248 to −0.039; P = .008).

These findings suggest that exposure to low levels of elemental sulfur produces a restrictive effect on children's lungs that is similar to the effect caused by early-life exposure to organophosphate pesticides, the authors say.

Dr Raanan and colleagues acknowledge the limitations of their study, including the challenge of performing spirometry in young children and the lack of available biomarkers to assess elemental sulfur exposure. They suggest that future studies should also aim to replicate the findings of the current study in other populations.

"Given the widespread use worldwide, we believe that the potential respiratory toxicity of elemental sulfur deserves more regulatory attention," the authors conclude.

This study was supported by grants from the National Institute of Environmental Health Sciences/National Institutes of Health, the US Environmental Protection Agency, and the Environment and Health Fund. One author has reported being a member of the US Department of Agriculture National Organic Standards Board, participating as a member of the Board for the Organic Center, and consulting with nonprofit organizations on the development of environmental health education curricula for child care providers. Another author has reported serving as a consultant to a nonprofit organization and as an expert witness on cases unrelated to the issues in this paper. The remaining authors have disclosed no relevant financial relationships.

Environ Health Perspect. Published online August 14, 2017. Full text

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