SOME 17 pupils from Ai Tong School in Bishan recently had to seek medical care for abdominal pain, vomiting and diarrhoea.
 
The illness was initially thought to have been caused by snacks they ate at a class party. It has now been ascertained that phthalates on a China-made toy that they had handled just before eating were the real culprits.

Phthalates are chemicals used to make plastics flexible. The specific ones found on the toy were dibutyl phthalates (DBP) and diethylhexyl phthalates (DEHP). The United States government has classified DEHP as a “probable human carcinogen” while the European Chemical Agency calls it a “Substance of Very High Concern”.

In the 1950s, it was adding DEHP to polyvinyl chloride (PVC) to render it flexible that made it more convenient to store and transport bags of blood for use in transfusions. Now phthalates are widely used to enhance fragrances in perfumes, nail polish, hairsprays and deodorants, as well as in lubricants and wood finishers.

That “new car smell” comes from phthalates vaporising from the dashboard if the vehicle has been in the sun. In the cool, they recondense as an oily film on the inside of the windscreen.

A US Centres for Disease Control and Prevention (CDC) survey last year of the levels of phthalates in our environment revealed that exposure to the chemicals was extremely widespread. Expressing concern over this, the US authorities stressed that DEHP was especially likely to cause serious problems in the development of the reproductive system in male babies and little boys.

The phthalates threat has acquired a fresh urgency because of a startling new insight into their mode of action. Conventionally, toxicologists consider what level of exposure to the agent in question is low enough to count as acceptable risk. The first dose to not elicit a response is used to draw the line. Logically, if a high dose elicits no response, then doses lower than that should not either. Thus testing doses below that threshold was deemed unnecessary.

But this is to assume a higher dose necessarily elicits a higher response, whereas it was shown in 2006 that low doses of phthalates can cause larger effects than higher doses. If so, what are considered to be dangerously high doses, cannot predict what might happen at low doses.

What this portends is that foetuses exposed to very low doses of phthalates may suffer far greater harm than we think possible based on safety standards established in the past using high dose studies. Such standards must now be deemed invalid.

Though somewhat counterintuitive, this phenomenon has also been observed in the endocrine (hormonal) system, where complex mechanisms are involved. Phthalates, in fact, act as hormone disrupters. In particular, DBP and DEHP disrupt aromatase, an enzyme that is crucial to the metabolism of sex hormones.

In sum, phthalates act as anti-androgens (or anti-male hormones). In pregnant women with levels of phthalates far below those conventionally thought to be toxic, male foetuses are 90 times more likely to have demasculinised genitals. Even the masculinisation of the brain in such foetuses is hampered.

In 2003, a Boston study confirmed that men with phthalate exposure had fewer sperm, which also tended to be weaker and more often deformed.

There is now an epidemic of male infertility in industrialised economies. Two common male birth defects seen are undescended testes and hypospadias (a penile deformity), both linked to low sperm count and testicular cancer in adulthood. All four conditions are related to disrupted hormone signalling during crucial periods of foetus masculinisation.

When all four conditions are found, the male patient has testicular dysgenesis syndrome, which is increasingly common in developed nations. In these countries, where phthalates are ubiquitous, it is disproportionately women of child-bearing age who are most exposed. A CDC survey had already uncovered this fact in 2000.

Soft PVC products contain over 40 per cent of phthalates by weight. PVC is widely used in packaging, mats, milk bottles, toys and so on. There is also a lot of skin contact with phthalates, especially in women’s use of personal care products like cosmetics, perfumes, soaps, shampoos, lotions and deodorants.

Children are directly at risk too. Phthalates that escape from PVC flooring and mats are breathed in, especially by those who spend a lot of time indoors. Baby powder, shampoo and lotion are particularly pernicious too. But toddlers chewing on softened plastic toys accounts for most of their exposure, according to Dutch and Danish studies.

Unfortunately, it is hard to avoid phthalates, for they are rarely listed on the ingredients label. However, “fragrances” may be a proxy term.

What you can do is microwave your food in pyrex instead of plastic. When using plastics, avoid those with recycling codes 3 and 7, which tend to contain phthalates.

The Health Sciences Authority has opined that phthalates in personal care products like soap are permitted here provided their amounts stay within the allowed levels. It said earlier in the year that “to date, there is insufficient scientific evidence to establish that they cause any health risk”.

It might be opportune to revisit those limits as soon as possible.