Josh Berson writes:

Cities are hard on the body. We are all familiar now with how dense living facilitates the spread of airborne disease. But the stressors of urban life are manifold. They include air- and waterborne pollution, noise, heat, light – and an excess of social contact. Pollution represents, as a 2017 report by the Lancet Commission on pollution and health puts it, ‘the largest environmental cause of disease and premature death’ among humans, responsible, in 2015, for ‘three times more deaths than from AIDS, tuberculosis, and malaria combined and 15 times more than from all wars and other forms of violence’ – and the burden will grow as wildfire becomes a year-round phenomenon. Pollution is neurotoxic, mutagenic and endocrine disrupting, to say nothing of its effects on breathing, vision, smell and touch.

Like factory farms and oil refineries, cities rely on surrounding areas to serve as pollution sinks. But, in most places, it is city dwellers themselves – and above all residents of low-income communities – who bear the brunt of the burden.

Then there is noise. Exposure to sound-pressure levels in excess of 90 decibels – common in restaurants – causes mechanical trauma to the hair cells of the basilar membrane. Even exposure at pressure levels long considered mechanically safe can, over time, yield irreversible changes in audition.

And the effects of noise extend beyond the auditory. Across a broad range of animal taxa, including mammals, chronic acoustic stress has been found to negatively affect reproduction, childhood development, metabolism, cardiovascular health, sleep, cognition and immune function.

Perhaps the most surprising risk of urban living is schizophrenia. The effect even exhibits a dose response: the more time you spend in cities, the greater your risk. The precipitating stressor appears to be at least partly social in nature, with the disenfranchised at highest risk. A mediating role has been hypothesised for danger-associated molecular patterns, signalling cascades that evoke inflammation in the absence of tissue trauma, as if in anticipation of injury. Spending time in green spaces lowers the risk.

Cities are good for many things, but minimising debility is not among them. [Continue reading…]