Elemental sulfur, which is the most widely used pesticide in California, and is also used in both conventional and organic farming in Europe, may harm the respiratory health of children living near farms where it is applied, according to new research led by UC Berkeley.

Previous studies on farm workers have shown the product can act as a respiratory irritant, but the Berkeley study is the first to look at communities living near to where the pesticide is used. Looking at children in an agricultural community of California’s Salinas Valley, researchers found significant associations between elemental sulfur use and poorer respiratory health. The study highlighted reduced lung function, more asthma-related symptoms and higher asthma medication use in children living less than a mile from recent elemental sulfur applications, compared to unexposed children.

The US Environmental Protection Agency (EPA) generally considers elemental sulfur as safe for the environment and human health, and over 21 million kilograms of elemental sulfur was used on agricultural land in California alone in 2013.

Commenting on the findings of the publicly-funded study, Dr Asa Bradman, from Berkeley’s school of Public Health, said, “Sulfur is widely used because it is effective and low in toxicity to people. It is naturally present in our food and soil and is part of normal human biochemistry, but breathing in sulfur dust can irritate airways and cause coughing. We need to better understand how people are exposed to sulfur used in agriculture and how to mitigate exposures. Formulations using wettable powders could be a solution.”

For the study, the research team examined associations between lung function and asthma-related respiratory symptoms in hundreds of children living near fields where sulfur had been applied, and compared their observations with a control group. The children were participants in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study - a longitudinal study, run in partnership between UC Berkeley and the Salinas Valley community, which has followed a group of children since birth to study the long-term impacts of pesticides on residents of farming communities. Most children in the study were born to families of immigrant farm workers.

The Berkeley researchers said they used regression models to factor other potential influences into their findings, like maternal smoking during pregnancy, season of birth, particulate matter air pollution, breast feeding duration and other variables.

Also commenting on the research, senior author Professor Brenda Eskenazi said, “This study provides the first data consistent with anecdotal reports of farmworkers and shows that residents, in this case, children, living near fields may be more likely to have respiratory problems from nearby agricultural sulfur applications.”

Given elemental sulfur’s widespread use worldwide, the study authors have said their findings merit further research and possibly even regulatory changes to limit the impacts of sulphur use on people’s respiratory health.

Reacting to the study, Chris Atkinson, Head of Standards at organic charity the Soil Association said, “The health impacts of high pesticide use on local residents as well as farm workers are sometimes overlooked and we hope that this American study will boost efforts to move towards more sustainable farming systems. The findings echo a recent UN report which found that excessive use of pesticides is dangerous to human health and the environment - and which concluded that it was misleading to claim that pesticides are vital to food security.”

Discussing implications for the UK, Chris said, “In the US, sulphur is widely applied to crops, primarily fruit and nut trees, by ‘fogging’ the trees.  This technique is one that requires a great deal of care to avoid the risk of spray drift. In the UK these crops are not widely grown due differences in climate, here sulphur is more likely to be used in field crops where different techniques which target sprays onto the plants are used.  All those applying any pesticide in the UK must follow strict rules to avoid spray drift and in most cases they must also have suitable training and qualifications which focus on the correct use and application.

“When it comes to organic farming, sulphur is one of a very small number of pesticides permitted in exceptional circumstances, and even then, only under strict conditions and where there’s no alternative to tackling a major threat to a farmer’s crops. Overall, organic farming has been found to help reduce the air pollution associated with farming practices by reducing emissions of sulphur and other substances.”