Candles May Be a Dangerous Source of Indoor Air Pollution

I've been lighting candles at home, as part of prayer. They create a wholly different atmosphere. 

I've seen candles used to awe-inspiring effect in Protestant church services (everyone holding a candle on Christmas Eve and singing "Hark the Herald Angels Sing") and Buddhist temple services (lit candles at regularly-spaced intervals along the altar while chanting the "Three Jewels" and the "Heart Sutra").

But, are candles safe--are they a source of indoor air pollution? This article say that there are potentially threatening information fails in the manufacture and supply chain and that even candles alleged to be safe haven't actually shown to be so. Certain churches and temples may be airy and spacious enough to mitigate the threat of inhaling pollutants, but else-wise?

In the absence of further qualifying information, not breathing smoke created by a burning substance of any kind would seem to be the wiser, though disappointing course.