Marijuana is seeing increased use both globally and domestically. However, the scientific community has not fully reached a consensus about what negative health effects and to what extent marijuana smoking may cause. In this study, we evaluated the associations between the body burdens of polycyclic aromatic hydrocarbons (PAHs) among marijuana smokers and the smoking heaviness. We observed clear, increasing trends of PAH body burdens as marijuana smoking increased. The findings highlight the importance of capturing the heaviness of marijuana smoking in future studies and support the need for well-designed toxicological and epidemiological studies for understanding the health effects of marijuana use in a changing environment.