Occupational heat exposure and the risk of chronic kidney disease of nontraditional origin in the United States

Abstract

Occupational heat exposure is linked to the development of kidney injury and disease in individuals who frequently perform physically demanding work in the heat. For instance, in Central America, an epidemic of chronic kidney disease of nontraditional origin (CKDnt) is occurring among manual laborers, whereas potentially related epidemics have emerged in India and Sri Lanka. There is growing concern that workers in the United States suffer with CKDnt, but reports are limited. One of the leading hypotheses is that repetitive kidney injury caused by physical work in the heat can progress to CKDnt. Whether heat stress is the primary causal agent or accelerates existing underlying pathology remains contested. However, the current evidence supports that heat stress induces tubular kidney injury, which is worsened by higher core temperatures, dehydration, longer work durations, muscle damaging exercise, and consumption of beverages containing high levels of fructose. The purpose of this narrative review is to identify occupations that may place US workers at greater risk of kidney injury and CKDnt. Specifically, we reviewed the scientific literature to characterize the demographics, environmental conditions, physiological strain (i.e., core temperature increase, dehydration, heart rate), and work durations in sectors typically experiencing occupational heat exposure, including farming, wildland firefighting, landscaping, and utilities. Overall, the surprisingly limited available evidence characterizing occupational heat exposure in US workers supports the need for future investigations to understand this risk of CKDnt.

Keywords: biomarker; Mesoamerican nephropathy; exercise; heat strain; heat stress.

Figure 1.

Proposed framework by which the magnitude of kidney injury experienced by US workers subjected to occupational heat exposure is modified by heat stress, nephrotoxins, and underlying risk factors for kidney disease. It is believed that frequent occupational heat exposures that elicit kidney injury progresses to chronic kidney disease of nontraditional origin. There is also potential that clinically diagnosed episode of acute kidney injury, which is typically subsequent to exertional heat stroke, may develop into kidney disease. *Magnitude/combination of heat stress modifiers, nephrotoxins, underlying kidney disease risk factors, and magnitude of kidney injury required to elicit chronic kidney disease of nontraditional origin in workers frequently exposed to occupational heat stress is not known.

Figure 2.

Climatically consistent regions within the contiguous United States identified by the National Centers for Environmental Information division of the National Oceanic and Atmospheric Administration (36). Figure created with MapChart (https://mapchart.net).