In animal tests, dibutyl phthalate has been shown to produce detrimental effects. The Environmental Working Group (EWG, http://www.ewg.org), a nonprofit environmental research organization, found that “DBP is a developmental and reproductive toxin that in lab animals causes a broad range of birth defects and lifelong reproductive impairment in males [when] exposed in utero and shortly after birth. DBP damages the testes, prostate gland, epididymus, penis, and seminal vesicles. These effects persist throughout the animal's life."
There are no similar studies or research showing any of that to be true (or false, for that matter) in humans. In 1985, the Cosmetic Ingredient Review (CIR) board (http://www.cir-safety.org/) deemed dibutyl phthalate safe for use in cosmetic products. In 2001, the CIR reviewed new data on the use of three phthalate esters (also known as phthalates) in cosmetics and on November 19, 2002 the CIR board announced its decision to not reopen the safety assessment of the dibutyl phthalate group of ingredients. Their summary on this issue states that “New data on acute and short-term toxicity were consistent with previously available data.” They went on to say “The developmental effects of phthalates seen in rodents raise questions about the potential for human health risk. However, these effects seen in rodents are at much higher exposure levels than humans are likely to encounter and they are subject to the species difference in the metabolism of phthalate diesters.” They also concluded that human exposure to dibutyl and diethyl phthalate was below the reference dose levels set by the U.S. Environmental Protection Agency. A more recent article examined several phthalate studies and concluded “that levels of concern are minimal to negligible in most situations…” (Source: Reproductive Toxicology, Volume 18, Issue 6, August-September 2004, pages 761-764).
The Cosmetics, Toiletries and Fragrance Association (CTFA) released a statement on November 19, 2002 concerning the Cosmetic Ingredient Review (CIR) Expert Panel's report that phthalates used in cosmetics (including nail polish) are safe. According to the CIR, the panel evaluated scientific research and compiled new data on diethyl (DEP), dibutyl (DBP), and dimethyl (DMP) phthalates. Dr. Gerald McEwen, Vice President of the CTFA, claimed the panel's decision was based on "solid science and not on speculation."
Despite the fact that the CTFA and CIR maintain phthalates are safe, the Food and Drug Administration (FDA), Health Canada, and other governmental health agencies around the world remain suspicious. Though the FDA and Health Canada have not restricted the use of phthalates, both agencies have made strong comments regarding their risk and safety. An FDA report, Aggregate Exposures to Phthalates in Humans stated that, "Manufacturers consistently argue that there is no evidence that anyone has been harmed by phthalates. As we note, however, and as confirmed by the NTP [National Toxicology Program] panel and FDA, no study has ever examined the impact of phthalates [on human reproduction] … Lack of evidence can hardly be used as evidence of safety when no one has ever [studied the issue on humans]."
The report went on to observe, “The increasing incidence of hypospadias, undescended testes, testicular cancer, and declining sperm counts in the US and many other parts of the world suggests that a closer look at many reproductive tract toxicants and endocrine disrupters is urgently needed in people. With respect to phthalates, however, evidence from relevant animal studies and from limited studies of non-reproductive tract impacts in hospitalized patients is sufficient to require phasing out the use of many of the phthalates." The Health Canada panel reached a similar conclusion, stating ‘the status quo is not an acceptable option.’" (Source: Aggregate Exposures to Phthalates in Humans, July 2002, http://www.fda.gov/ohrms/dockets/dailys/02/Dec02/120502/02d-0325-c000018-02-vol1.pdf). This explains why many cosmetic companies (including those solely making nail polish) are actively seeking alternatives to phthalates. It could be argued that, at levels presently used, phthalates pose no health risk. Although there is no concrete human evidence to suggest phthalates are harmful, the lack of studies in this area continues to leave the issue open to debate and indicates a “better safe than sorry” approach is wise.