In a review of all the products used for cleaning by the cleaning industry, "clean-smelling" air fresheners seem to pose little risk. Unfortunately, the "fresh" scent of air fresheners may disguise not only undesirable odours, but may mask a health hazard as well. Chemicals known as phthalates (pronounced thal-ates) can be present in air fresheners are known to cause hormonal abnormalities, birth defects, and reproductive problems. Individuals whose line of work puts them into frequent contact with these chemicals are at a greater risk of developing long term health problems simply by the nature of their occupation, for example, janitorial and cleaning staff.

NRDC (the National Resource Defense Council) which is an international non-profit environmental organization conducted an extensive independent test on 14 commonly used air fresheners. The NRDC discovered phthalates were in 86 percent (12 of 14) of air freshener products tested, including those marketed as "all-natural" or "unscented". It was noted that none of the products tested listed phthalates on their labels. The NRDC recommends that government regulators should follow up by doing more thorough tests on these products and enact basic measures to limit exposure to these chemicals, in the interest of public health. Meanwhile, it may be prudent to avoid prolonged and frequent exposure to air fresheners. Extreme precaution should be used when using air fresheners in places where children and pregnant women are likely to frequent

Unpleasant odours are generally undesirable in any closed environments. Odours are not the cause of toxicological concern, but odours may increase the reporting of symptoms (for example, nausea, headache, eye and throat irritation).

Unfortunately, the rise in popularity of air fresheners has fast outgrown awareness of the potential health threats from exposure to the chemicals they may contain. Most phthalates are now understood to interfere with production of the male hormone, testosterone, and have been associated with reproductive irregularities. A variety of animal studies have tied prenatal exposure to certain phthalates with decreases in testosterone, malformations of the genitalia, and reduced sperm production. Studies on humans have show that phthalates have been associated with changes in hormone levels, poor semen quality, and changes in genital development. Five phthalates-including one found in air freshener products-are listed by the State of California as chemicals "known to cause birth defects or reproductive harm." Phthalate exposure to a closed environment has also been linked to allergic symptoms and asthma. Since there are no labeling requirements, even so called "natural" products can contain toxic chemicals. Detection of these ingredients is virtually impossible by the people who unknowing buy these products.

While the focus here is on the presence of phthalates in air fresheners, it is worthwhile mentioning that researchers have detected other chemicals of concern to human health in these products as well. The European Consumers' Organisation, BEUC (Bureau Europen des Consommateurs), commissioned a study in January 2005 to analyse the chemical substances present in indoor air following the use of air fresheners (including incense, natural products, scented candles, gels, aerosols, liquid and electric diffusers. The BEUC study found volatile organic compounds (VOCs) in these products at high levels and concluded that VOCs significantly contributed to indoor air pollution. In particular, the European study detected cancer-causing chemicals such as benzene and formaldehyde in some air fresheners. Benzene is known to cause leukemia in humans, and formaldehyde has been linked to cancers of the upper airways. The majority of products also contained allergens (such as limonene). People with allergies to these chemicals could have adverse reactions, including rashes or even asthma attacks, from exposure to air freshener products.

Air fresheners are rarely necessary simply because they cannot substitute for good ventilation. The best solution is to open windows to bring in fresh air or to use fans to maintain proper air circulation. Air fresheners also are not the solution to poor air quality; they mask bad odours, however they very almost never eliminate their cause.

Avoid using air fresheners if possible, but when necessary, use products with the lowest levels of phthalates to limit exposure to these toxic chemicals, or use products that are certified by organizations such as Environment Canada's Environmental Choice Eco Logo or the United States' Green Seal Programs as being an environmentally responsible product.

Just remember this, until manufacturers fully disclose all ingredients on product labels, each and every time you inhale fumes expelled by air fresheners, the risk of developing certain health problems is more concerning than any perceived benefit of using the product.