27 Ways Climate Change Heat Events Can Kill You
Why we should decarbonize our economy.
Events of extreme heat pose a threat to human life. In the 2003 European heat wave over 70,000 deaths occurred, 10,000 during the Russian heat wave of 2010, unfortunately extreme heat waves are quite common (Mora, Counsell, Bielecki & Louis, 2017). The geographic extent of heat events is increasing with climate change and rising global temperatures (Mora, et al., 2017).
Climate conditions that prevent the body from losing heat, ie too hot, too humid and particularly both occurring together, cause the body to make physiological responses, potentially resulting in death.
A survey was conducted of PubMed and Google Scholar database articles for physiological mechanisms and vital organs affected by extreme heat. Five physiological mechanisms, ischemia, heat cytotoxicity, inflammatory response, disseminated intravascular coagulation, and rhabdomyolysis, were triggered by extreme heat. Seven organs were impacted, the brain, heart, intestines, kidneys, liver, lungs, and pancreas (Mora, Counsell, Bielecki & Louis, 2017).
27 different pathways were found to lead to organ failure and death as shown in the table below.
When the human body starts to become heat stressed the hypothalamus causes blood vessels to dilate to enable more blood to flow near the skin, in order to lose heat, but this may result in insufficient oxygenated blood flow to the core, resulting in ischemia (lack of blood flow) and hypoxia (lack of oxygen).
Excess heat can exceed the cell thermal tolerance, breaking down cell membranes and is called heat cytotoxicity.
Hypokalemia, a potassium deficiency caused by sweating and urination, can lead to the fragmentation of the myocardium, the heart muscle, increasing the risk of cardiac arrest.
Prolonged systemic inflammatory response can lead to organ damage and leakage.
Systemic inflammation and injury of the vascular endothelium can enable disseminated intravascular coagulation causing excess blood clotting and lack of blood flow.
Rhabdomyolysis, from heat cytotoxicity, ischemia, or hypokalemia, is the break-down of skeletal muscle cells, releasing myoglobin, which can cause acute renal failure by clogging fine kidney tubes.
The heat wave induced, multiple ways to die are summarized in this table.
As is often the case, those with a compromised thermoregulatory capacity, ie the old, young, and sick, and people with limited socioeconomic capacity, ie the poor and the isolated, are at far greater risk (Mora, Counsell, Bielecki & Louis, 2017).
Air conditioning will limit heat exposure but this will not be available to everyone, and when present will effectively trap people indoors and make power failures deadly. Greening cities should be an immediate goal to provide some degrees of cooling, which may indeed be lifesaving.
27 Ways Climate Change Heat Events Can Kill You, is clearly quite depressing but it illustrates that we need to half our emission of greenhouse gases by 2030 and have zero emissions by 2050.
References:
Mora, C., Dousset, B., Caldwell, I. R., Powell, F. E., Geronimo, R. C., Bielecki, C. R., … & Trauernicht, C. (2017). Global risk of deadly heat. Nature climate change, 7(7), 501–506.
Mora, C., Counsell, C. W., Bielecki, C. R., & Louis, L. V. (2017). Twenty-seven ways a heat wave can kill you: deadly heat in the era of climate change. Circulation: Cardiovascular Quality and Outcomes, 10(11), e004233.
