Most people have heard about phthalates and that they should be avoided but do not actually know what they are. Phthalates are plasticizers used to increase the flexibility of plastic polymers, primarily polyvinyl chloride or as we know as #3 plastics. Use of phthalates accounts for about 70% of plasticizer use in the plastic industry. There are right around 25 types of phthalates used in the market, but there are four that account for most usage: DBP: di-n–butyl phthalate, DINP: diisononyl phthalate, DIDP: diiosodecyl phthalate, DEHP: di-2-ethyl hexyl phthalate. DEHP usage has been estimated to account for about 50% of all phthalate applications. As a society, we produce around 5 million tonnes of phthalates of which right around 2 million tonnes is DEHP alone.
Phthalates are produced by reacting phthalic anhydride with various alcohols to form a generalized ester of 1,2-dibenzo-dicarboxylic acid. By varying the alcohols used, the side chain of the generalized ester form will vary, and in turn gives; each phthalate its chemical properties. It is generally assumed that phthalates with side chains that are branching (not linear) and have less than six carbon atoms in their side chain structures are at a higher risk of leaching from plastic products. Now many industry informational videos and brochures state that phthalates cannot leach from products, but that is in fact not that case. Phthalates primarily work by creating gaps and spaces between the high molecular weight plastic polymers, by creating these spaces the polymer is softened, and flexibility is increased. This is the goal of phthalates, after all, to increase the flexibility so if they were actually bound to the polymers the desired degrees of flexibility could not be achieved. It has also been documented in many studies that phthalates leach from a variety of products. In most products, it is estimated about 4% of the phthalates can leach under normal use and that up to 15% of DEHP may leach from medical products. Factors that may accelerate leaching are the age of the products, exposure to heat and the products surface area. Phthalates can leach into the air, food and water from products.
So what are some products that contain phthalates? Well again your #3 plastics broadly but more specifically inks, paints, vinyl flooring, personal care products (make-up, lotions, shampoos, tampon applicators, etc…), medical devices (blood bags, medical tubing), food packaging, detergents, children toys, some foods and pharmaceuticals (time-release medicines, gastro coating products). In some personal care products, phthalates are listed as parfum or fragrance. An online database EWGs Healthy Living is a useful site in which you can find information on an array of products and what chemicals are in them and what researchers know about those chemicals.
Okay, so we are aware phthalates are used in high volumes and in numerous products so why do we care about them? They are a concern as exposure to phthalates during fetal stages may alter the development of the reproductive system and changes during early developmental years may have impacts on later reproductive health. The US EPA has even employed the term “Phthalate syndrome” to refer to alterations in the fetal development of the reproductive system. Okay, so how did we come to these generalized ideas?
Well to start work in rat and mice models noted that maternal exposure to male fetuses could significantly alter testosterone levels and the AGD in young. AGD is known as anogenital distance, the distance from the anus to the base of genitalia. In males, especially in non-human mammalian species, a decrease in AGD is a reliable indicator of feminization during development. Researchers started to take note that male rat and mice exposed during development and prepuberty exhibited delayed spermatogenesis, abnormal Sertoli cells (cells in testes that nourish and support sperm), decreased testosterone levels, decreased AGD, decreased levels of insulin-like factor 3 and anti-Müllerian hormone. These last two factors are key in the descent of testes and prohibiting the development of Müllerian tubes (fallopian tube precursor) in male fetuses. It was also noted that these effects could be carried over into adulthood and impair fertility. In utero exposure to phthalates may also increase incidences of hypospadias (urethra opening is on the underside of the penis) and cryptorchidism (undescended testes).
There are a number of studies that look at various aspects of phthalate toxicity, so a recent summary of available data concluded that effects appear to occur through three main pathways. First is that phthalates can alter thyroid and growth hormone pathways which can alter development and growth. Second is alterations in cholesterol transport in cells. Cholesterol is required for steroidogenesis, especially the production of testosterone and estrogen. Changes in the timing and amounts of those hormones could have effects on reproductive health. Finally, is the activation of PPAR (peroxisome proliferator-activated receptors) and generation of reactive oxygen species (ROS). Excess ROS are harmful in the body as they can disrupt cell membranes, damaging cells as well as damaging DNA.
So what all does this really mean? Ultimately, research has demonstrated that exposure to phthalates in laboratory animals indicate that exposure may lead to significant alterations in the reproductive health of those organisms. What about in humans? We cannot test on humans, so we rely on studies that correlate levels of phthalates in blood, urine, amniotic fluid and breast milk to observed effects in the individual or offspring. So just to make clear correlation does not mean causation! We are complex organisms who at any given time may have upwards of 200 chemicals in our blood that can all have detrimental effects. We use results of animal studies to support strong correlations in human surveys to generate data that is then used to make regulatory decisions. Now, back to humans, correlations with increased phthalates levels have been linked to changes in reproductive health and development, neurological development and behaviour in children, thyroid function, asthma and allergy responses, obesity, and incidences of breast cancer. Greatest interest has been placed on infants receiving medical care (NICU) due to their exposure from medical supplies, as well as toddlers. Toddlers are often a point of focus in risk assessments, as they are prone to place all sorts of objects and dirty fingers in their mouths.
Where are we regarding regulations and phthalates? Well Europe’s REACH program has taken the most action in understanding and regulating phthalates, this is due in part their “precautionary principle”. This principle is a great thing and in simplicity requires that the manufacturer must prove that the product is safe before it can enter the market and if there is doubt then that product is not ok to enter the market. In North America, the burden of proof is not the manufacturer but to the public’s tax dollars and researchers. Some view that approach as people and the environment essentially being the test subjects (just a little food for thought there). Back to REACH and their program, so many phthalates have been allowed for use in plastics, others are banned from children’s toys, and some are still pending final categorization. In the US, various agencies have attempted to limit the type and amount of phthalates in children toys and some pharmaceuticals. US EPA has listed three phthalates in the Endocrine Disruptor Screening Program. In Canada, there have been some restrictions on the amount used in children toys. Australia also has some regulations in place.
My final opinion on all this is that phthalates do present a potential risk especially to fetuses and young children. Is it the end of the world that exposure happens, no but if actions can be taken to decrease exposure then it should and that goes for all synthetic chemicals in my very own personal opinion. So what can you as an individual do to control your exposure? Ditch the plastic, quit buying one-time use plastics, and bring your own cloth shopping bags, bamboo utensils. As a society, we produce around 270 million tonnes of plastic annually and promptly throw 275 million tonnes away each year. We use close to half of our total annual oil consumption just to produce plastics. Many of those plastics (30-50%) are intended for only a single use. By moving away from plastic products, you will immediately start to decrease your potential for exposure and do the environment an excellent service. Another way is to be conscious of your personal care products, buy scent free, or those specially listed to not contain phthalates, parfums or fragrance. Better yet make your own products and store them in glass jars. Hopefully, soon I can find the time get my listed posted in how I’ve reduced our plastic usage at home.
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