In the News: Phthalates

By Michael Pickering

While reading the NY Times one morning in March, I came across an article titled “A Plastic Threat to Male Fertility” in the Science Times section. Having encountered phthalates in the past, I was curious to read further.

Federal researchers recently spent four years tracking 501 couples who were trying to have children. The goal of their study was to assess the impact of everyday chemicals on fertility. While both men and women were exposed to known toxins, men appeared much more likely to suffer fertility problems as a result.

“Anything you can think of that’s testosterone-dependent is likely to be affected.”   – Heather Patisaul, North Carolina State University

The gender disparity was most significant when it came to phthalates. This group of petrochemicals finds its way into many commercial products. Phthalates are among a group of compounds known as endocrine disruptors. As the endocrine system controls the production and distribution of hormones in the body, they have been implicated in a range of health problems. Unlike many of the study’s other industrial toxins that bio-accumulate, phthalates are metabolized within hours of ingestion. However, their pervasiveness in the environment means almost constant exposure, which increases their impact.

Among the myriad uses for phthalates are as plasticizers (rendering polymers flexible rather than brittle) and in cosmetics, where they improve smoothness of flow upon application.

Partial List:

  • Cosmetics
  • Plastics
  • Household products
  • PVC pipes
  • Hospital tubing
  • Medicine (pills, capsules)
  • Air filters, residential and commercial

While the evidence for an effect on male fertility is compelling, it is still difficult for researchers to gauge the full impact these prevalent phthalates are having. If you want to minimize your exposure, read labels, do not heat anything you intend to ingest in plastic, and bring your own glass to the keg party.

IN THE PAST: Phthalate Blues

Personally, my formal introduction to phthalates was when I quit teaching high school and went to grad school. My research involved isolating and characterizing secondary metabolites in the plant family Rutaceae. The process involved solvent extraction (soxhlet) and evaporation followed by gravitational silica column chromatography. We learned quickly that all the bulk silica, most of the solvents, and the most popular clear flexible tubing (Tygon) all contained di-octylphthalate (DOP), an oil. The air in the building was also loaded with DOP due to the filters. Fortunately, it was easy to keep track of DOP because of its blue fluorescence. The low polarity of the plasticizer made it easy to elute off of the columns with the slurry solvent. For our 20cm x 20cm x 1-2mm thick layer prep plates, we formed and dried them, and then placed them in the chromatography chamber with acetone. Upon re-drying, the plates viewed under UV light were flat white with a bright blue edge along the top.

Most of my targeted metabolites are fluorescent; yellow, green, pink, and blue to the eye. I once inadvertently isolated a non-chromophoric terpene because I was chasing an indigo blue fluorescent spot on the TLC. Upon elution from the plate, I got an oil. Mass spectrometric analysis revealed the terpene in a tableau of DOP fragments. The friend who ran the mass spec for me, Charlie, was in charge of a spectroscopy lab for a veterinary toxicology department at the time. He said he could recognize all the spectrographic manifestations of DOP from twenty paces.

My last encounter with DOP was several years later, in a Pickering customer’s lab. An extremely agitated gentleman had called to announce that he had “NO PEAKS!!!” So, our customer service chemist went for a visit, and I went along for the ride.

We arrived at 10:00am, and fortunately the system was running. He had a Carbamate post-column instrument paired with a water/methanol two-pump, four-piston binary gradient HPLC. The pistons were ganged in series. Our chemist engaged the customer while I observed the instrument. The fluorometer was so overloaded with signal that the PM tube was regularly turning off. There was no troubleshooting information available from the magnitude of the signal, but there was a very regular and periodic spike, implying a piston cycle.

Upon further observation of the HPLC, I noticed that both reservoirs’ contents had traveled up into the Nitrogen lines and was sloshing around in the Tygon tubing. With this back-flowed solution being sloshed back into the reservoir periodically, I realized the problem. Although Tygon tubing is phthalate-free today, it was loaded with DOP back then. The swamping fluorescence was in both reservoirs. The spike frequency was the last piston on the methanol pump, where the DOP concentration would be the highest.

The customer had his peaks, he just couldn’t see them for the bright lights.