Deadly pesticide’s ‘safety measure’ does not prevent deaths, a breakthrough study shows

A new study, led by the Centre for Pesticide Suicide Prevention (CPSP), has found no evidence that the inclusion of a vomiting agent in a highly toxic pesticide helps to save lives.

Following a series of deaths due to unintentional ingestion, a vomiting agent named PP796 was added to standard paraquat products in the 1970s.

Paraquat is one of the most commonly used herbicides worldwide. It is also highly poisonous and fatal to humans when ingested. The manufacturer claimed that this safety measure would help to prevent deaths by stimulating vomiting and reducing absorption to the gut.

The Food and Agricultural Organization (FAO) subsequently adopted the manufacturer’s formulation for its international specification, which includes a requirement for more than 50% of patients to vomit within 30 minutes.

This is the first high-quality clinical study to explore whether the vomiting agent fulfils the FAO specification and, more importantly, prevents deaths from paraquat poisoning.

Addressing serious data concerns

The research is significant as no previous study, including those conducted by the manufacturer, has provided sufficient data to address whether the dose of PP796 in standard paraquat products is effective in preventing deaths.

A recent examination of all published and unpublished evidence has identified errors in previous data interpretation.

This study was conducted in collaboration with the South Asian Clinical Toxicology Research Collaboration in Sri Lanka. It involved data collection from 10 hospitals and over 400 patients who had self-poisoned with paraquat.

Data was collected on dose ingested, time of exposure, the circumstances of the poisoning (accidental or intentional) and the incidence and timing of vomiting after ingestion. Details of treatment and patient outcome were also recorded.

Results show poor outcomes for patients

The study found that 69% of patients vomited within 30 minutes of ingesting the pesticide, therefore fulfilling the FAO specification for more than 50% of patients to vomit within 30 minutes.

However, the proportion of patients vomiting within 30 minutes increased to 82% for the highest ingestion group. This suggests that vomiting is a marker of higher doses of paraquat ingested, not a result of the added agent.

Furthermore, the study found that patients who vomited were more likely to die. 82% of patients who vomited within 30 minutes died, compared to 54% of patients who either did not vomit or vomited after 30 minutes.

The ‘only effective way’ to prevent deaths

Professor Michael Eddleston, who led the study, said:

“When PP796 was introduced to paraquat products in the mid-70s, the primary aim was to prevent unintentional deaths. However, an effective vomiting agent should also prevent many of the deaths that occur from low-intent self-poisoning, since small doses are often ingested in spontaneous acts of self-harm. However, despite fulfilling the FAO’s requirement to induce vomiting within 30 minutes, our research clearly shows that PP796 has little impact on a patient’s chance of survival.

Inaccurate data, and subsequent claims that PP796 is an effective safety measure, has allowed paraquat products to remain on the market in many countries. This is despite the lack of any credible evidence proving that the measure actually saves lives.

Paraquat remains an extremely dangerous pesticide for which there is no antidote. The only effective way to prevent deaths from paraquat poisoning is to restrict access through regulation, replacing it with less harmful alternatives.”

Previous research by Centre for Pesticide Suicide Prevention has shown that country restrictions on paraquat have contributed to a reduction in deaths, with no adverse impact on agriculture or food production.

The study is published in Clinical Toxicology.