Testing hair from Asian monkeys living close to people may provide early warnings of toxic threats to humans and wildlife, according to a study published online this week in the American Journal of Physical Anthropology.
In parts of South and Southeast Asia, macaques and people are synanthropic, which means they share the same ecological niche. They drink from identical water sources, breathe the same air, share food sources, and play on the same ground.
"Macaques are similar to humans anatomically, physiologically and behaviorally," said the senior author on the study, Dr. Lisa Jones-Engel, a senior research scientist at the National Primate Research Center at the University of Washington in Seattle.
"They are also similar in their response to toxic exposures," said lead author Dr. Gregory Engel, a physician at Swedish Cherry Hill Family Medicine in Seattle and a research scientist at the UW National Primate Research Center. When macaques live in environments polluted by motor vehicles, openly disposed garbage, and industrial waste, they can come into contact with toxic substances such as lead, just as their human neighbors might.
Lead toxicity, the authors noted, remains a significant public health problem around the world. Intense exposure to lead can damage the nervous, circulatory, and reproductive systems, as well as the kidneys and liver. Exposure during childhood, according to other studies, may cause more subtle effects, such as decreased intelligence.
According to Jones-Engel, the researchers hypothesized that young macaques, in particular, would be good sentinels for human exposure to lead exposure.
"Young macaques share a propensity for curiosity and have a penchant for picking up objects and inserting them into their mouths, just as young children do," Jones-Engel noted. "A juvenile macaque has all the curiosity and energy of a toddler, and then some! Plus their parents aren't well informed about environmental hazards."
She and her team of primatologists, physicians, epidemiologists, veterinarians and toxicologists decided to test urban macaques as a potential early indicator that their human neighbors, especially the children, are being exposed to lead and other toxic metals. They took hair samples from three groups of free-ranging macaques at the Swoyambhu temple overlooking Kathmandu, Nepal. The macaques patrolling the site have abundant contact with people and with human-made environments. This World Heritage Site temple is located in a densely populated urban area with poor infrastructure that leaves point sources like discarded lead batteries, flaking leaded paint, and lead contaminated soil, a by-product of decades of leaded fuel, in the environment.