Portfolio 21 does not invest in companies involved exclusively in the tobacco industry, or in diversified companies that derive more than a small percentage of revenues from the production of tobacco. According to the World Health Organization, tobacco kills up to half of its users and consumption of tobacco products is increasing on a global basis, particularly in low and middle income countries. Cigarette smoke contains a complex mixture of over 4000 chemicals, over 60 known to cause cancer. These chemicals are produced by the burning of tobacco and its additives. Many tobacco companies purchase their tobacco leaves from large suppliers located in emerging markets where labor, safety, and environmental regulations are rarely enforced. The lack of regulations, combined with the labor and resource intensity of this crop, exposes farm workers to pesticide and nicotine poisoning while creating biodiversity and land pollution concerns.