Marijuana and the Cannabinoids

Effects of Marijuana on Immune Defenses 253
Chapter 11
Effects of Marijuana on the Lung
and Immune Defenses
Donald P. Tashkin and Michael D. Roth
1. INTRODUCTION
Cannabis has been used as a drug for thousands of years, but marijuana smoking
has become prevalent in Western society only during the last 40 years (1,2). An annual
survey conducted in the United States from 1975 to 2002 documented that marijuana
is now the second most commonly smoked substance after tobacco (1,2). Marijuana
smoke, like tobacco smoke, is generated by the pyrolysis of dried plant leaves. As a
result, it shares thousands of chemical features in common with tobacco smoke,
including qualitatively similar amounts of carbon monoxide, cyanide, acrolein, benzene,
vinyl chlorides, aldehydes, phenols, nitrosamines, reactive oxygen species (ROS),
and a variety of polycyclic aromatic hydrocarbons (3,4). The primary distinction
between marijuana and tobacco is the presence of ∆ 9 -tetrahydrocannabinol (THC) and
other cannabinoids in Cannabis vs the presence of nicotine in tobacco (3,4). Although
the hazardous effects of tobacco smoking have been extensively documented and
include emphysema, chronic obstructive pulmonary disease (COPD), heart disease,
and risk for developing several different types of cancer, studies on the health effects
of marijuana smoking are less abundant. The common perception is that marijuana
smoke is less toxic and that smoking a few marijuana joints per day has far fewer
consequences than smoking a pack of tobacco cigarettes (5). However, the lack of
filtering and differences in the smoking technique associated with marijuana use result
in an approximately fourfold greater deposition of tar particulates in the lung than
occurs from smoking similar amounts of tobacco (6). In addition, the concentration of
pro-carcinogens such as benz-[α]-anthracene and benzo-[α]-pyrene are up to twofold
higher in marijuana tar (3,7). The presence of irritants and pro-carcinogens in mari-
From: Forensic Science and Medicine: Marijuana and the Cannabinoids
Edited by: M. A. ElSohly © Humana Press Inc., Totowa, New Jersey
253