Sasiistock via Getty Images Researchers say climate change is leaving kids more susceptible to things like heat stroke and asthma.

When parents talk about climate change, they often stress their fear for their children’s futures. But it turns out the consequences of global warming, which can sometimes seem far away, are already affecting children’s lives.

A new guidance document, published by the Canadian Paediatric Society (CPS) on Wednesday, has found that children are more vulnerable than adults to the effects of climate change.

“The younger the child is, the more at risk they are to the effects of climate change. Children are still growing and developing rapidly. This makes them more vulnerable,” Dr. Irene Buka, the article’s principal author, told HuffPost Canada.

WATCH: More women are choosing not to have kids, because of climate change. Story continues below.

In the article, Buka describes climate change as “the single, largest global health threat of the 21st century.” She notes the vast number of potential infections and health conditions, which children are more susceptible to, that can emerge from increased air pollution, heat waves, water pollution, and other natural hazards.

This susceptibility means they’re more vulnerable to things like allergies, heat exhaustion and heat stroke, asthma, and heart disease, as well as other food-, water- and vector-borne illnesses. (The World Health Organization estimates more than 88 per cent of diseases attributable to climate change are occurring in children younger than five.)

“Children metabolize more water, more air, and more food per kilogram of body weight than adults,” says Buka. “So if there’s a pollutant in our food, or in our milk, then children are more likely to be affected by that pollutant than an adult might be.”

Environmental changes are already happening here

Buka also worries that physicians are not well-equipped to notice when a patient’s illness might be climate-related, because their medical training doesn’t necessarily account for it. “When you see a child with a fever, most of the time, it’s a common cold,” she says. “But it’s important to now consider there might be other things going on, because the world is a changing place.”

Buka worries that certain climate-related health issues won’t be identified as such, because they would be easy to shrug off as being unrelated to warming temperatures. But certain infections — Lyme disease, for example — are actually becoming more common specifically as a result of warming temperatures, since northern climates (which used to be prohibitive for organisms carrying those bacterium) are getting warmer, allowing ticks and other infection-carrying organisms to spread to new areas.

WATCH: How to stay safe in a heat wave. Story continues below.

And since they spend more time outside and are simultaneously in development, kids are vulnerable to those illnesses.

The World Health Organization, a partner of the clinic where Buka works, has previously explained how children are particularly vulnerable when a disaster — ie. climate change — strikes.

At the Children’s Environmental Health Clinic, the only clinic of its kind in all of Canada, Buka says she regularly fields concerns from parents worried about their kids’ susceptibility to climate-related illness.

What parents can do to help keep their kids safe

This year, the non-profit Ontario Public Health Association (OPHA) launched the Make It Better campaign, which was designed to offer tips to parents who might be concerned about their kids’ vulnerability to climate-related illnesses.

Asthma, the site notes, has become more common in children — alongside other respiratory diseases — as a result of air pollution. The OPHA suggests children avoid exercise or exercise indoors when outside air quality is poor; avoid highly-polluted settings like high-traffic areas; and consider using HEPA filters, which remove toxins from polluted air.

To prevent Lyme disease, the OPHA suggests using bug spray that contains DEET or icaridin; wearing closed-toe shoes, long sleeves and pants; and to always shower or bathe within two hours of being outdoors. It also lists a number of other recommendations, should a child be bitten by a tick.

Children are among the most vulnerable to heat-related illnesses, like heat exhaustion and heat stroke. To make sure kids keep cool during extreme heat, the OPHA recommends parents have their kids play in the shade, rather than in direct sunlight; have them drink plenty of water throughout the day; and try to move activities to cooler hours.