Thirty canine companions participated in the study, wearing silicone tags attached to their collars. This pooch belongs to first author Catherine Wise. (Photo courtesy of Catherine Wise)

Pet dogs could shed light on how human exposure to chemicals can lead to disease. A first-of-its-kind study by NIEHS grant recipients from North Carolina State University (NCSU) and Duke University found similar levels of chemicals in dogs and their owners through the use of silicone monitoring devices. Scientists detected substances ranging from phthalates, which are used in plastic products, to pesticides such as chlorpyrifos.

The fact that people and their canine companions share living spaces — and many biological attributes — makes this research especially important, according to the authors. The pets potentially offer great insight into ways that chemicals in the home may affect a person’s health. This study was published June 16 in Environmental Science and Technology.

“In humans, it can take decades for clinical signs of chronic diseases resulting from exposures to become evident,” said corresponding author Matthew Breen, Ph.D., an NCSU genomics professor. “Due to dogs’ shorter lifespan, emergence of such diseases may occur in just a few years. Given that reduced latency period, studies like this, on a large scale, could help identify at-risk human populations and allow for exposure mitigation, early diagnoses, and intervention.”

“We once used canaries to warn of dangerous gases in mines. Now, we are turning to dogs, our closest companions, to assess potential risks associated with our daily exposures,” said Breen, center, shown with two of his graduate students. (Photo courtesy of NCSU Veterinary Medicine)

Benefits of silicone monitoring devices

Researchers studied 30 households from North Carolina and New Jersey, measuring chemical levels in dogs through silicone collar tags. Owners wore silicone wristbands. Such devices absorb a variety of chemicals, and it is believed that they effectively capture real-world exposures, which involve different mixtures and routes of transmission.

“A major advantage of using pet dogs as sentinels is that they are companions to people across all socioeconomic statuses and are impacted similarly,” said Wise. (Photo courtesy of University of Southern Maine)

“Silicone monitoring devices are non-invasive, inexpensive, temperature-stable, and convenient to wear,” said first author Catherine Wise, a graduate research assistant in Breen’s lab. “They have immense potential to be used in a variety of settings and study populations where alternative approaches may not be feasible.”

Detecting commonly used chemicals

Of 41 substances that met certain detection thresholds, 32 were shown to be significantly correlated in both dogs and humans. Those chemicals fall into the following classes.

• Brominated flame retardants — Found in electronics and furniture, among other products.
• Organophosphate esters — Used as flame retardants and plasticizers.
• Pesticides — Eliminate pests from crops and deter bugs in homes. Also found in flea and tick treatments for pets.
• Phthalates — Some plastics, building materials, and personal care products contain these substances.
• Polychlorinated biphenyls — Chemicals in caulking, adhesives, fiberglass, and more.

“I was particularly surprised to find that dogs and their owners had such similar chemical exposures,” said co-author Heather Stapleton, Ph.D., a Duke University professor. “It really highlights that our exposure to many chemicals occurs in the home.”

Screening dogs for other substances

“We observed a strong correlation between the chemical levels measured on the dog tags and those detected in urine, suggesting the tags captured exposures well,” said Stapleton. (Photo courtesy of Duke University)

“Our study includes a six-month follow-up monitoring period, along with a canine cancer screening test,” said Wise. “As we expand, we will repeat the screening periodically, including when a dog moves to a new home, to look for changes,” she noted.

Wise added that going forward, she plans to assess exposure to per- and polyfluoroalkyl substances, which are found in nonstick cookware and stain-resistant fabrics, among other goods.

“This is a really exciting and important proof-of-principle experiment,” said co-author Alison Motsinger-Reif, Ph.D., head of the NIEHS Biostatistics and Computational Biology Branch. “Dogs have served as an important model system in pharmacology, and expanding that system into toxicology is an important next step.”

Citation: Wise CF, Hammel SC, Herkert N, Ma J, Motsinger-Reif A, Stapleton HM, Breen M. 2020. Comparative exposure assessment using silicone passive samplers indicates that domestic dogs are sentinels to support human health research. Environ Sci Technol 54(12):7409-7419.

(Jesse Saffron, J.D., is a technical writer-editor in the NIEHS Office of Communications and Public Liaison.)