It’s all a matter of language, in the end. Take toiletries: what the manufacturers might term “personal care products”, scientists such as Khang Huynh of the Department of Biosystems and Agricultural Engineering at Michigan State University, US, could call “emerging organic contaminants”.
In particular, the team has looked at an antimicrobial compound known as triclocarban (TCC). The compound was recently banned in the US an ingredient in soaps, but remains widely used in other care products. TCC has been shown to be present in hefty quantities in treated wastewater, much of which is used to irrigate crops.
As early as 2009, TCC was discovered to be an endocrine disruptor. In 2017, scientists established that the compound passes through both the placenta and milk ducts from mothers to offspring, and showed that in a mouse model both mothers and pups carrying TCC were heavier than unexposed individuals. This raised questions of whether the compound interfered with fat metabolism.
Despite the concerns regarding the effects of TCC – echoed in Europe as well as North America – comparatively little is known about how it moves through the food chain.
To try to gain insight into the question, Huynh and colleagues established a crop of jalapeno pepper plants (Capsicum annuum), grown hydroponically. The plants were given water which contained TCC – some of it standard, and some with the radioactive isotope carbon-14 added.
After 12 weeks, samples were taken from the plants’ roots, stems, leaves and fruit. The researchers found that TCC was present throughout the plant. Much of it had been absorbed into cell walls. Unexpectedly, in the fruits up to 90% of the TCC had been metabolised, meaning that it had become soluble and bio-available.
Huynh and his colleagues express concern over their findings.
“Because pepper fruits are commonly eaten fresh, human exposure to both TCC and its metabolites through the consumption of contaminated products is expected,” they write.
Their warning, however, is tempered by a couple of caveats. The fact that much of the TCC is incorporated into the plant cells walls, they note, may be protective, because the human digestive system is unable to break down cellulose efficiently.
They also note that there has been very little research to date exploring the effects of metabolised TCC on human health.
Such lack of data, however, is no cause for complacency.
“The overall toxicity of TCC and its soluble metabolites merits discussion in assessing the human-health risks of consuming contaminated food crops,” they conclude.