Cytotoxic Effects of N,N-Diethyl-Meta-Toluamide (DEET) on Sinonasal Epithelia

Comparison of the cytotoxicity and zebrafish embryo toxicity of insect repellent ingredients: p-Menthane-3,8-diol synthesized by green chemistry from Eucalyptus citriodora and N,N-diethyl-meta-toluamide

Bio-sourced insect repellents are becoming more popular due to their safer applications. Known for its strong fly-repellent property, Cis, trans-para-menthane-3,8-diol (PMD) is the main component of the lemon eucalyptus essential oil and is synthesized from citronellal. In April 2005, US Centers for Disease Control approved two fly repellents that do not contain N,N-diethyl-meta-toluamide (DEET), including PMD. Due to the intentional and pervasive human exposure caused by DEET as insect repellent, concerns have been raised about its toxicological profile and potential harm to people. We hypothesized PMD would have a different toxicological profile than DEET. We synthesized PMD from Eucalyptus citriodora using green chemistry methods and analyzed its structures by 1H-NMR,13C-NMR, and GC/MS spectral methods. We used MTS assay to determine the percentage inhibition of PMD and DEET on keratinocyte (human epidermal keratinocyte [HaCaT]) cells. The xCelligence system was used and followed at real time. Effects of PMD and DEET on zebrafish embryo development were monitored and levels of lipid peroxidation, glutathione-S-transferase (GST), superoxide dismutase (SOD), and acetylcholinesterase (AchE) were evaluated at 72 h post-fertilization using spectrophotometric methods. Our results showed that while DEET inhibited human keratinocyte cell growth, while imporved cell viability and proliferation was exposed in PMD exposed group. In zebrafish embryos, PMD was less toxic in terms of development, oxidant-antioxidant status, and AChE activities than DEET. Based on these results we suggest an efficient method using green chemistry for the synthesis of PMD, which is found to be less toxic in zebrafish embryos and human keratinocyte cells.

Recent advances in degradation of N,N-diethyl-3-toluamide (DEET)-an emerging environmental contaminant: a review

N,N-Diethyl-3-toluamide (DEET) is a commonly used insect repellent, which acts as an organic chemical contaminant in water and considered as an emerging contaminant which has been observed worldwide. It gets discharged into the environment through sewage waste. The various methods have been used to degrade DEET, such as UV based, ozonation, photocatalytic degradation, and biodegradation (based on the metabolic activity of fungi and bacteria). However, less research has been done on the degradation of DEET by deploying nanoparticles. Therefore, biodegradation and nanotechnology-based methods can be the potential solution to remediate DEET from the environment. This review is an attempt to analyze the routes of entry of DEET into the atmosphere and its environmental health consequences and to explore physical, chemical, and biological methods of degradation. Furthermore, it focuses on the various methods used for the biodegradation of the DEET, including their environmental consequences. Future research is needed with the application of biological methods for the degradation of DEET. Metabolic pathway for biodegradation was explored for the new potent microbial strains by the application of physical, chemical, and microbial genomics; molecular biology; genetic engineering; and genome sequencing methods.

Residential Proximity to a Commercial Pesticide Application Site and Risk of Chronic Rhinosinusitis

Importance

Environmental and occupational toxicants have been shown to be associated with an increased prevalence of chronic rhinosinusitis (CRS). However, few to no studies have evaluated patients for CRS using objective testing and workup protocols that fulfill guidelines for CRS diagnostic criteria. Furthermore, no study, to our knowledge, has investigated the risks of CRS in the context of residential exposure through proximity to a commercial pesticide application site.

Objectives

To evaluate associations of residential proximity to a commercial pesticide application site and the prevalence of CRS with nasal polyps (CRSwNP) and without nasal polyps (CRSwoNP).

Design, Setting, and Participants

This was a retrospective cohort study of patients who presented to a tertiary care institution for rhinology evaluation between March 1, 2018, and December 31, 2022.

Main Outcomes and Measures

The outcome variable was the clinical diagnosis of CRS (CRSwNP, CRSwoNP, or non-CRS control). Patients' residential addresses were utilized to determine pesticide exposure status based on a validated computational geographic information algorithm based on data from the California Pesticide Use Report System. The dichotomous independent variable of exposure status (exposed or non-exposed) was determined by assessing reports of any pesticide applications within 2000 m of each participant's residence in 2017. Multivariable logistic regressions assessing CRS status and CRS subtypes were conducted with pesticide exposure as the primary covariate of interest. The primary study outcome and measurements as well as study hypothesis were all formulated before data collection.

Results

Among a total of 310 patients (90 CRSwNP, 90 CRSwoNP, and 130 control), the mean (SD) age was 50 (17) years; 164 (53%) were female. Race and ethnicity information was not considered. Controlling for patient demographic information, smoking history, county of residence, and medical comorbidities, pesticide exposure was associated with an approximately 2.5-fold increase in odds of CRS (adjusted odds ratio, 2.41; 95% CI, 1.49-3.90). Pesticide exposure was associated with similar risks for CRSwNP (adjusted relative risk ratio [aRRR], 2.34; 95% CI, 1.31-4.18) and CRSwoNP (aRRR, 2.42; 95% CI, 1.37-4.30).

Conclusions and Relevance

The findings of this retrospective cohort study and analysis revealed that residential exposure to commercial pesticide application within a 2000-m buffer was independently associated with an approximately 2.5-fold increase in odds of being diagnosed with CRS. If validated by additional research, this association would have substantial implications for public health.