Safety/Security

Introduction

Although poisoning by DEET (active ingredient of the most common commercial repellents) and D-limonene are rare events, it is known that these two substances may be toxic. The absorption of high concentrations of DEET (N, N-diethyl-m-toluamide) can have neurotoxic effect and even be lethal (1,2,3,4,5). D-limonene, if ingested in high concentrations may also cause death (6).

Therefore, we conducted a simple test on an eukaryote model to compare the effect of the two substances on beans development (Phaseolus vulgaris,Fabaceae).

Methods

In order to reduce fungal contamination, water and cotton used in the experiment were sterilized by autoclaving. Beans seeds were immersed in 2.7% hypochlorite and then in 70% ethanol (5 minutes for each solution). The seeds were divided into 5 groups corresponding to five different treatments), each containing 16 individuals. Each seed was placed on a piece of cotton inside a plastic cup. The groups were placed on a bench in order to receive the same illumination.

All seeds initially received 2 mL of water. Treatments were initiated after 24 hours. We adapted limonene concentrations (Limonene 1 - non lethal; Limonene 2 - lethal) to seeds size, according to a prior study of toxicity reported by (6). The following treatments were administered every 24 hours:

Experiment was initiated in August 11th and treatments lasted from August 12th to 20th.

Analysis of results

Beans development

At the end of the experiment, all individuals in each group were measured, as seen below:

There was a significant difference between the growth of limonene 1 and control groups compared to the group receiving DEET and limonene in higher concentration, as already noted (6).

Figure 1: Differences between beans seedlings development under different treatments. Different letters above the error bars indicate significant differences at the 0.05 level using Kruskal-Wallis test followed by post-hoc pairwise multiple comparison test according to Nemenyi. Statistical inferences were made using R package.

Conclusions

Control 1 and 2 groups, as well as Limonene 1 did not affect beans development. DEET toxicity was confirmed, once nether beans nor fungi were able to develop in the group treated with the repellent containing DEET. Treatment with high concentrations of limonene also affected the development of seeds.

Notes

It is important to report some observations during the experiment: (1) plastic cups containg bean seeds were corroded by repellent with DEET; (2) we observed fungi development around the seeds under all treatments, except in DEET group. We believe those observations reinforce DEET toxicity.

References

1. ROBBINS P. J., CHERNIAK M. G. Review of the biodistribution and toxicity of the insect repellent N, N-diethyl-m-toluamide (DEET). Journal of toxicology and environmental health, 1986.

2. OSIMITZ T. G., MURPHY J. V., FELL L. A., PAGE B. Adverse events associated with the use of insect repellents containing N, N-diethyl-m-toluamide (DEET). Regul Toxicol Pharmacol., 2010.

3. MCGREADY R., HAMILTON K. A., SIMPSON J. A., CHO T., LUXEMBURGER C., EDWARDS R., LOOAREESUWAN S., WHITE N. J., NOSTEN F., LINDSAY S. W. Safety of the insect repellent N, N-diethyl-m-toluamide (DEET) in pregnancy. Am J Trop Med Hyg. 2001.

4. BARR D. B., ANANTH C. V., YAN X., LASHLEY S., SMULIAN J. C., LEDOUX T. A., HORE P., ROBSON M. G. Pesticide concentrations in maternal and umbilical cord sera and their relation to birth outcomes in a population of pregnant women and newborns in New Jersey. Sci Total Environ, 2010.

5. WILES D., YEE J., CASTILLO U., RUSSELL J., SPILLER H., CASAVANT M. A Lethal Case of DEET Toxicity Due to Intentional Ingestion. Journal of Analytical Toxicology, July 6, 2014.

6. KIM, W. Y.; KIM, M. J.; CHUNG, B. Y.; BANG, D. Y.; LIM, S. K.; CHOI, S. M.; LIM, D. S.; CHO, M. C.; YOON, K.; KIM, H. S.; KIM, K. B.; KIM, Y. S.; KWACK, S. J.; LEE, B. L. Safety evaluation and risk assessment of D-Limonene. Journal of toxicology and environmental health, August, 2013.