This article is part of a 6-day series titled "Toxicants in Consumer Products". The authors, with background knowledge in environmental toxicology, will delve into the most pressing ecotox issues of today.
Phthalates. The word doesn’t exactly roll easily off your tongue, and it conveys no meaning beyond the rather unusual spelling. When I look at it, I always think that I’ve put in too many h’s. Are there two….four? It does, however, catch the eye and pulls attention back to it. By the time you’ve spent thirty seconds on the pronunciation, you start to wonder about its meaning. Besides being a word that could bring even the most confident thirteen year old speller to his or her knees, it represents an important class of compounds that pose an interesting toxicological problem. Phthalates show toxicity, but are found abundantly in consumer products, cosmetics and plastics. We have tested for their effects, and we know a lot about them, but we can’t quite put enough of a case together to run these phthalates out of town, torches burning, pitchforks in the air – despite the best efforts of a few groups.
Over the last 15 years, a great deal of research has been published on the adverse health effects of phthalates to living organisms and, as a result, regulations for their use have been amended several times. Alternative compounds have been found for uses which produce the highest exposure levels to the most sensitive populations. Despite these measures, phthalates are still readily employed in the manufacturing, food, and personal care industries. Also, as tests are performed, more questions arise with each positive result found, which exemplifies the experimental limitations of the tests themselves. Unfortunately, we can’t test phthalates directly on human beings, and our test systems contain important faults which reduce their biological relevance.
This article aims to inform the casual reader beyond what’s being trumpeted in the news. What are phthalates? What toxicological effects do they cause in the body? Are they worthy of the bad press and increased regulations? This final question looms heavy on my mind as I drink my carbonated beverage from a plastic straw…out of a plastic cup…while putting on sunscreen before a day on the beach. I want to believe what I read and denounce these phterrible phthalates! But can I?
Phthalates are currently a hot topic news item. The Washington post recently reported an article that asked the question about whether phthalates and parabens are harmful in makeup and lotions. The author came up with an answer popular with many in the toxicology field, “a very clear maybe”. Different types of phthalates are roughly separated into low and high molecular weight members, and these differences affect not only the chemical properties of the molecule but also the toxicological consequences from exposure.
So why even produce these things in the first place? Phthlates are incredibly useful industrially, and production has increased with the increasing amount of plastics available world-wide. Their primary uses are to soften plastics and act as lubricants. However, they are not covalently (permanently) linked to any these substances, and therefore have the ability to leach out into the surrounding environment. This can be directly observed by the fragile nature of some older plastics, which fracture and become brittle due to the absence of phthalates within the material. High molecular weight phthalates are used in the manufacture of flexible vinyl which is incorporated into flooring and wall coverings, food contact applications, and medical devices. Low molecular weight phthalates are found in many cosmetics, like perfumes and lotions, as well as in industrial solvents, varnishes, and lacquers. The many beneficial uses for phthalates in everyday life can result in high occupational and recreational exposure to these molecules. Although the general population experiences high levels of exposure (since we all use plastics and some kind of cosmetic), it hasn’t translated into excessive toxicity because our body handles phthalates efficiently.
Toxicity data regarding phthalates is abundant but still somewhat ambiguous, which is important due to the aforementioned broad application and high exposure to these molecules. It is important to again reinforce that not all members of the phthalate family produce the same level of toxicity, and there are marked species differences in sensitivity to phthalates.
Of greater concern to the general population is their endocrine disrupting potential. Developmental and reproductive endpoints observed in animal studies found associations between some phthalates, and their metabolites, on male and female sexual organ development, time to puberty, regulation of the oestrus cycle, and delayed ovulation. These endpoints were produced with higher doses, and some questions remain about the validity of these results upon extrapolation to humans.
I believe that data on the effects from phthalate exposure is sound, and the mechanism of action combined with the results of animal studies paint a pretty bad picture for these compounds. These negative results have been extensively exploited by the media. However, to properly assess these molecules, we have to focus on concentrations at the target site. As a population, our exposure to these molecules is quite high, and all of us will show phthalate metabolites in our urine. However, our bodies deal with these compounds efficiently and excrete them rapidly. While some toxicity data on occupational exposure and sensitive populations is concerning, the general public does not appear to be threatened. This may be a result of confounding factors in our experimental models, but may also be a real testament to the metabolic capabilities of our wonderful livers!
While I would never call phthalates ‘safe’, I don’t believe that we can crucify them as a family of compounds. Certain members of the phthalate family could be avoided, and sensitive populations including children and pregnant women, are at higher risk. As adults however, we are able to process phthalates efficiently and their many beneficial uses precludes these segregated toxicological concerns.
I don’t see enough data to overly concern me about their effects on my health. I’m not part of the sensitive population, and I have normal metabolism to detoxify my every day exposure levels. I’ll still drink from my plastic cup, and put on my lotion, thank you very much! But hey, that’s just what I phthink!