In September, the Natural Resources Defense Council (NRDC) warned consumers to avoid exposure to the phthalate, which helps fragrances linger after application, citing animal studies indicating that it affects growth and food consumption.
The environmental lobby group also said DEP, when mixed with other phthalates, affects hormone levels, semen quality and genital development.
In an information sheet entitled 'The Truth About Phthalates', the FMA accused the NRDC of misrepresenting the evidence, arguing that none of the cited studies indicates that there are any negative effects of using DEP as a fragrance ingredient.
Backing up its argument, the FMA pointed out that a review completed in March by the European Commission's Scientific Committee on Consumer Products (SCCP) confirmed that DEP is safe for use in cosmetics.
The FMA said the chemical profiles of different phthalate compounds differ significantly, which explains why the DEP is considered safe in Europe while the phthalates DBP and DEHP are banned in the continent.
In the further defense of its position, the FMA mentioned the supportive stance of the Cosmetic Ingredient Review Expert Panel, which is composed of scientists publicly nominated by industry, government and consumer groups.
The panel concluded in its peer reviewed literature report two years ago that DEP is safe for use in cosmetic products at current concentration levels.
The conclusions reached by the FMA are in line with study results published by the American Chemistry Council's Phthalates Esters Panel last month.
Published in the periodical Environment Science and Technology, the study found no indication that DEP affected hormone levels.
The authors said they hoped the scientific evidence would dispel speculation from pressure groups linking the phthalate to damage to the reproductive organs.
Lobby groups, led by the Environmental Working Group (EWG) have been campaigning against the use of phthalates in personal care products for years.
It argues that many beauty consumers use multiple products in parallel, leading to a potentially dangerous cumulative effect in the bloodstream.