Tuesday, April 18, 2017

The Next Climate Change Epidemic

It's potentially lethal and it's spreading to workers throughout Central America. It's a mysterious kidney disease attacking labourers.

Scientists have identified certain key themes. The majority of people with the unexplained disease are men, and it strikes predominantly in hot, humid regions where people are engaged in strenuous outdoor labour: farming, fishing or construction work. Dehydration, which seems an obvious factor, causes acute kidney disease that is easily reversed by drinking water, rather than this chronic form. This has left two burning questions: what causes this new form of kidney disease, and will it be likely to spread as the world gets warmer?

Meanwhile, in El Salvador over the last two decades, more and more patients have arrived at clinics and hospitals, often taxing them to their limit. Many people, unable to get treatment, simply return to their homes to die.

This is really a silent massacre,” says Ramon GarcĂ­a-Trabanino, a Salvadoran kidney specialist.

many agricultural labourers don’t admit to getting ill, even to themselves. But kidney disease is a sneaky opponent. It can totally destroy one kidney while the individual remains blissfully unaware. Only in the final stages of the disease do the workers get a hint that all is not well, and by the time they arrive at the emergency ward, they are dying.

Garcia-Trabanino started a fellowship at the Rosales hospital as a young doctor in 1998, and what he encountered resembled a scene from a battlefield. He had expected to be treating heart disease, neurological patients, eye problems – the full gamut of medical conditions. Instead all he encountered were men dying – sometimes slowly, but usually quickly – from kidney failure. They came in such numbers that they overwhelmed the beds and spilled into the corridors.

Hunting the killer.

Richard Johnson of the University of Colorado learned of the mysterious Central American killer at a conference in Canada in 2011. He began to hunt for the cause. At first he suspected a link to field hands rehydrating with sweet soda to avoid drinking unsafe, contaminated water. That didn't pan out. He then began to suspect that daily exposure to high heat coupled with constant dehydration were to blame.

Johnson took his theory to the lab, where his team put mice in chambers and exposed them to hours of heat at a stretch. One group of mice was allowed to drink unlimited water throughout the experience, while a second group had water only in the evenings. Within five weeks the mice with a restricted water intake developed chronic kidney disease. During the day, loss of salt and water caused the mice to produce high levels of fructose, and crystals of uric acid would sometimes form as water levels dropped in their urine. When the scientists disabled the gene that metabolises fructose and repeated the experiment, neither group developed chronic kidney disease.

For Johnson, a clue as to why the epidemic is escalating came from a disturbing occurrence during his research with Garcia-Trabanino. One day, when the field researchers were measuring uric acid levels, only seven workers showed up for work. “But they all had uric acid crystals in their urine. All of them,” Johnson says. “It was bad news for these seven.”

Alarmed, he contacted the lead investigator of the study, who felt that the team should ignore the finding as so few workers had turned up that morning. “But I said that maybe this is the most interesting group, because 100 per cent of the workers got it that day.”

He looked up the weather and found out that it had, in fact, been the hottest day of the year at the study location. “Suddenly a really, really big heatwave came in and the workers weren’t ready,” he says. “They went out because they were expecting it to be a relatively normal day and they got hit.”

Instead of his usual fare of nephrology and diabetes papers, Johnson began to pore over global maps of climate and solar radiation. The rise in average temperatures over the last few years in Central America had been incremental, but the number of extreme events had gone up disproportionately. “And, by gosh, the areas that have the highest solar radiation and heatwaves are overlapping the places right where the epidemics are.”

He contacted climate experts at the nearby National Oceanic and Atmospheric Administration in Boulder, Colorado. They verified and finessed his original discovery, and the team published an assessment report in May last year, which suggested a connection between climate change and the epidemic. Johnson says it “may well be one of the first epidemics because of global warming”.

Climate change brings dire predictions of extreme weather and sea-level rise in the future, but it is affecting the world’s most vulnerable populations right now, he says. And although heat exposure can affect the body in many ways, our kidneys are in the first line of attack, as their role is to keep electrolytes within the normal range and blood volume stable. “We predict the kidney is going to be one of the prime targets as heat increases.”

This could get a great deal worse and very soon. Central America is expected to be one of the first regions hit by "climate departure" which marks a transition to a new climate in which every year thereafter is hotter than the hottest year experienced previously. Every year will be a scorcher.  This is expected to set in through the tropics beginning the middle of the next decade and then spreading to the rest of the world by 2047.

We know that climate change is already killing the poorest and most vulnerable people. Tell me then why is our prime minister so hell bent on a massive expansion of bitumen extraction and export? Harper made Canada a pariah on climate change. Wasn't one Harper enough?


Toby said...

"Tell me then why is our prime minister so hell bent on a massive expansion of bitumen extraction and export?"

Because he can afford air conditioning?

Mound, I wonder if part of the dehydration problem is related to salt depletion. I don't imagine many peasants carrying salt tablets to combat the heat.

The Mound of Sound said...

From what I read, Toby, there doesn't appear to be any link between salt depletion and the kidney failure they're experiencing. I have worked jobs (admittedly back when ships were made of oak and men were made of iron) where we had to take salt tablets a minimum of twice a day so I'm not discounting that issue/factor.