Uncovering the Hidden World of Terpenes in Everyday Life

Terpenes are a class of ubiquitous chemicals with many potential health benefits and harms. Human exposure to terpenes can occur through pathways such as cleaning products, fragrances, diet, or drug-use. α-pinene, β-pinene, and limonene are known to be present in trees, citrus fruits, herbs, marijuana, and cigarette smoke. With little known about human exposure to these compounds, it was important to characterize the baseline level of exposure for the general U.S. population. Using results for 2213 samples for participants 6-80 years with surplus serum available from NHANES 2013-2014, obtained with previously published quantitation methods, we compared serum terpene concentrations in demographic groups and identified likely exposure routes. Multiple linear regression found smoking 10-19 cigarettes per day (CPD) was associated with 35.8 % higher serum limonene and smoking >19 CPD was associated with 44.9 % higher serum limonene compared with non-smokers with no secondhand smoke exposure (p = 0.0002). In addition, we found that recent consumption of citrus-rich foods (rates per 1 kg consumed) was associated with significantly higher serum α-pinene (32.8 %, p = 0.0042) and limonene (82.1 % p = 0.0002). Finally, we observed significant associations between serum terpenes and demographic groups. Females had significantly lower serum limonene (p = 0.0243) compared to males. Hispanic and non-Hispanic Asian people had significantly higher serum β-pinene (p < 0.05) and limonene (p < 0.05) compared to non-Hispanic White people. This work characterizes the baseline of terpene exposure in the general U.S. population.