Climate instability: A silent (?) threat to public health

I have attended conferences where climate change was discussed from a food security angle. Increasing temperatures, drought, excess rain, and flooding would lead to food shortages. Therefore, climate-smart food sources must be incorporated into planetary health diets so that people get their nutritional needs while keeping their impact on the planet at a minimum.

During Solano County's Public Health Division-Wide Meeting this year, Mr Jerry Huber (Director, Department of Health and Social Services) and Dr Bela Matyas (Public Health Officer and Deputy Director, Department of Health and Social Services) highlighted the need to talk about climate instability from a public health perspective. This encompasses the associations between public health and clean water, public health and **exotic** disease-bearing vectors, and public health and wildfires, among others.

Zooming out of these specific links to public health reveals that climate instability is the underlying common theme. Climate instability is not a silent threat, as people probably make it out to be, but it is not loud enough for people who deny it. The saddest part is that the people most affected by climate instability are also the poorest, and the people who deny that the climate has become more unstable tend to be more economically advantaged.

So, how is public health associated with climate instability? I read up about this after the Division-Wide Meeting. There is a lot of information from the academe about the impact of climate instability on public health. Some examples include:

The rise of vector-borne diseases

Vector-borne germs are spread to humans by different animals. For example, mosquitoes spread dengue virus (which causes dengue fever), Plasmodium sp. (which causes malaria), West Nile Virus (which causes West Nile fever), and St Louis Encephalitis Virus (which causes St Louis encephalitis). Ticks can carry Borrelia burgdorferi (which causes Lyme disease), Rickettsia spp. (which causes Rocky Mountain Spotted Fever and tick-borne encephalitis), and Coxiella burnetii (which causes Q fever). Fleas may transmit plague (caused by Yersinia pestis). 

The geographic spread of vector-borne germs highly depends on the habitats of the vectors. For example, the mosquitoes that carry dengue, Aedes aegypti, were initially found in Africa. Warming temperatures have widened the distribution of this mosquito species: it can now be found in areas that used to be too cold for it.

The reddening of the sea

When I was living in the Philippines, I learned that we're supposed to avoid eating shellfish (e.g., mussels, oysters, clams) during the warmer months (March to November) because algal blooms occur when the coastal seawater is warm. These algal blooms involve the rapid population growth of Pyrodinium bahamense and Gymnodinium catenatum. Along the Pacific West Coast, the algal blooms are predominated by Alexandrium catenella. These organisms cause paralytic shellfish poisoning. 

A scientific study published in 2021 reported that the USA has documented an increasing trend of harmful algal bloom events over the years. The emergence of Pyrodinium bahamense in Florida highlights the geographic expansion of toxin-producing algal species. For some species, ocean warming has been attributed to the geographic spread. The increase in the diversity of organisms and toxins and the increase in harmful algal blooms increase the chances of people eating infected shellfish. Moreover, local health jurisdictions will increasingly keep beaches and recreational waters off-limits to prevent people from getting infected by toxins produced in these algal blooms.

The scorching of the earth

Climate instability is linked to the increasingly larger wildfires occurring in California. As I write this, CalFire recorded over 2000 wildfires in 2024. The land area affected this year is about 13 times bigger than last year.

Wildfires deteriorate air quality. I remember taking Donan for a walk in September 2020 when the SCU lightning complex fires raged in the Diablo Range. Thick smoke darkened the sky, and ash fell. We returned to the house because the bad air quality could affect Donan's weak respiratory system. Aside from respiratory illnesses, wildfires are associated with eye irritation, adverse birth outcomes, cardiac arrests outside hospitals, premature mortality, and mental health burdens.

As I listened to Dr Matyas and Mr Huber, I realized that climate instability is not quite a quiet threat. It's always front and centre; however, people tend to focus on such a zoomed-in view of climate (e.g., temperature and public health) that it's easy to miss the big elephant in the room, so to speak.