The top five countries that export candles to the US are China, Taiwan, England, Hong Kong, and Mexico. Limited discussions with some industry representatives indicate that there are probably many more very small manufacturers. The top five countries that export incense to the US are India, China, Thailand, Japan, and Hong Kong. In the scientific literature we reviewed, zinc and tin were found not to be emitted at concentrations that would raise concerns when burned indoors. Sooting can occur when combustion conditions are impaired when burning candles.
Scented candles are more likely to produce soot than unscented candles.
Sooting can cause property damage by blackening surfaces. We could not identify any studies on potential human health effects associated with soot from candles. Several studies indicated links between exposure to incense smoke and health effects, including cancers and contact dermatitis. A few studies indicated possible mutagenic and genotoxic effects. Studies that examined the emissions of specific contaminants from incense smoke indicated that benzene and particulate matter may be emitted at concentrations that could pose human health risks.