In a new study, scientists have determined that testing hair from Asian monkeys living close to people may provide early warnings of toxic threats to humans and wildlife.
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 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.
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. Plus their parents aren't well informed about environmental hazards," she said.
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.
Hair lead levels differed among the three groups of macaques, and were much higher in younger macaques.
The researchers' data did not support the idea that these lead levels were from basic differences in the animals' diet, and instead suggested that, in this population of macaques, behavioral or physiological factors among young macaques might play a significant role in determining exposure to lead and subsequent tissue concentration.
"Chemical analysis of hair is a promising, non-invasive technique for determining exposure to toxic elements in free-ranging, non-human primates, and further multidisciplinary research is needed to establish whether it can be used to predict lead levels in humans who live in the same areas," the research team concluded.