Thursday, December 17, 2009

The Health Impacts of a Changing Climate

What the future will look like – without all the doomsday prophecies.

It’s hard to go through the day without hearing someone mention climate change, how you should be reducing your carbon footprint, or noticing the cute sustainability slogans on t-shirts at the mall.

What’s even harder is trying to wrap your mind around what climate change could really mean for us. The ice caps are deteriorating, and the annual average temperature is on the rise, but it’s hard to gather what that means for regular people.

The way it’s usually framed is by saying there will be more hurricanes, flooding, and mass hysteria.

Dr. Peter Berry studies the human health impacts of climate change for Health Canada. He said, “because climate change is very complex, and climate scientists are trying to project decades into the future, there is a certain amount of uncertainty about what to expect.”

Berry said increases in severe storms, hurricanes and other natural disasters are our best prediction of what will come about from climate change, but they are not guaranteed changes.

What is pretty well assured is a rise in temperature, and increased precipitation levels. In most of Canada it will be warmer, and rain more often.

Berry and the Health Canada team said simple things like more rain and warmer days can lead to serious health threats. The kind that could affect your daily life, not just natural disasters.

Berry said one of the often overlooked issues of global warming is the warming itself. Heat waves can be a serious health threat, especially for certain vulnerable sub-sets of society.

A warm spell is considered a heat wave if the temperature for three consecutive days is over 30 degrees Celsius.  With the average temperature going up, these events will become more common.

For instance in London, Ont., the average numbers of days in the year with a temperature above 30 degrees is nine. In 2002, London hit that level 23 times. It is estimated that we will see such scorchers 36-plus-times per year in 2050.

The high heat puts your body under stress as it tries to maintain a safe internal temperature. For a lot of people, a cool glass of lemonade and some rest and relaxation will get you through. But for some, it’s not always so relaxing.

“Seniors are at particular risk for heat-related illness and death because heat tolerance and thermoregulatory capacity decrease with age,” said Health Canada in the report Human Health in a Changing Climate: A Canadian assessment of vulnerabilities and adaptive capacity.

The difficulties seniors can have when dealing with increasing heat is of particular concern for Canada:
·         In 1981, ten per cent of Canadians were over 65.
·         In 2005, that level rose to 13 per cent.
·         In 2036, it is expected that 24.5 per cent of us will be over 65.

Berry said the best way to protect yourself from heat waves is to seek out air conditioning. Or, if you don’t have a/c, hunt down the “cooling centres” Health Canada is pushing for.

Dr. John Howard, chair of the Canadian Association of Physicians for the Environment (CARE) said the method Health Canada is advising isn’t the best long term strategy.

“In the mitigation of heat, what happens is we consume energy. So it’s a… reinforcing cycle,” he said.

Having people crank the a/c when it gets hot will help protect them from heat waves, but the strategy would ultimately speed up climate change, he said.

As long as the energy source to power the air conditioners leads to the release of green house gases, cooling centres are a short term strategy to fix symptoms, rather than attacking the underlying problem.

Another problem Berry said we will run into with higher temperatures and more precipitation is increases in some diseases.

“Canada lies at what is currently the northern margin for efficient transmission of most arboviruses, so disease outbreaks tend to be rare and have historically tended to occur in late summer,” said the Health Canada report.

Arboviruses are diseases transmitted by invertebrate vectors like mosquitoes, ticks and sand flies, which are collectively known as arthropods.

The ranges in which these animals are active, and the times of year when they are out, are in part controlled by the temperature. Having a higher average temperature could lead to expanded ranges and population sizes, said Health Canada.

“We are seeing an expansion in vector numbers are they are moving northward,” said Health Canada.

In Canada, arthropods are well known for transmitting diseases like West Nile virus and Lyme disease. Having the bugs out longer would likely lead to more cases of these diseases, as well as the other diseases they could harbour.

The Health Canada report said that there is a possibility exotic diseases like dengue fever, malaria, and eastern equine encephalitis could be brought into Canada.

In addition to increasing the range of many vector-borne diseases, the elevated rainfall levels will also be problematic.

Increases in precipitation levels will lead to higher volumes of water running over the surface. The water can pick up chemical or biological contaminants and carry them to the nearby sewer, stream, or aquifer.

These contaminants can be nearly anything: oil, road salt, pesticides, fertilizer or other animal wastes. When these products reach bodies of water, they can trigger algae blooms, or aid the growth of water-borne pathogens like E. coli, Giardia, or Shigella.

In 2001, the Walkerton, Ont. E. coli outbreak was preceded by increased levels of rainfall, which led to the contamination of groundwater sources, said Health Canada. It was one part of a set of issues which led to seven deaths and 2,300 people becoming ill.

The protections against these diseases are mostly handled through infrastructure. It seems likely that, with a little work, our health institutions and infrastructure should be able to adapt to these changing conditions.

But, if the increases in flooding, severe storms, and hurricanes being predicted holds true, then infrastructure systems like waste treatment stations and hospitals may not be able to keep up.
With the number of unknowns facing us with climate change, Dr. Howard of CARE thinks we need to take a different approach to fighting it.

“I think we need to be individually more responsible. I think we often say were going to leave it up to somebody else all the time. We have to reduce our energy use; we have to look at other ways of transportation. We need to do it individually. We need to do it collectively,” said Howard.

The health issues outlined by Dr. Berry and Health Canada were those we can expect with even the most conservative understanding of climate change.

Dr. Robert Lannigan, a professor of microbiology and medicine at the University of Western Ontario said we need to change our outlook on climate change if we want to stay healthy.

“Climate is the biggest driver of human health. We are a part of the ecosystem, not apart from it,” he said.

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