Costa Rica

Costa Rica

Kidney function in rice workers exposed to heat and dehydration in Costa Rica


The land of dreams, beaches, and nature. Costa Rica is in the world's view for several good reasons. A stable economy, long lasting democracy, and the lack of armed forces make Costa Rica a prime tourist destination. The country is also well known for their passionate football culture. Following the stellar performance of the Costa Rican team in the FIFA World Cup of 2014, defeated by Netherlands in the penalty round, the team has grown and now produces exceptionally talented footballers.

True to its history, the 2022 Costa Rican NephroWorldCup unit doesn't shy away from big scientific challenges either. This year's team focuses on how human exposure to the changes in climate effect kidney function. Researchers collected data and surveys over a three month period in 72 male participants (Box 1). The study subjects are unique in that they were rice workers at one particular company in which the rate of CKD of unknown origin (CKDu) is high (Carousel 1). Each month, blood and urine, along with health questionnaires were completed. Workers were then separated into field workers (n = 27) and various other occupations (n = 45).

Box 1: The company that was analyzed in this study employed 104 males and 2 female rice workers at the start. Incomplete surveys and laboratory data values resulted in a total of 72 subjects: all male.

CKDu - NephroWorldCup

Carousel 1: CKDu in Latin America | Presented at the 2021 World Congress of Nephrology | Courtesy of Drs. Marvin Antonio Gonzalez and Carlos Orantes.

In this day and age of climate change, Costa Rica has been leading the pack as a country that relies on renewable energy. It is only natural that the country focuses on how heat exposure can affect kidney health. An important measure of studying heat exposure on kidney function is the the wet bulb globe temperature (WBGT). The WBGT measures heat stress under direct sunlight exposure. It takes into account several factors such as

  1. wind velocity,

  2. humidity, and

  3. cloud shadow.

Multiple agencies use this method to evaluate external working conditions to which employees are exposed (Video 1). The researchers in this study used the WBGT in their assessment of CKDu. The measurements were taken in the areas where the study subjects were working. Researchers compared actual heat exposure to OSHA recommendations; the latter considered as the safe levels of heat exposure under which one can work. Needless to mention, this unique measure is uncommonly seen in nephrology-focused studies and is only one of the reasons why the Costa Rican team enters the NephroWorldCup as strong contenders.

At enrollment, the field workers had a lower eGFR compared to other workers (4% versus 19%, respectively). Field workers also experienced more incident kidney injury than their non-field counterparts (26% vs 2%, respectively). The prevalence of an elevated serum creatinine (>1.25 mg/dL) was significantly greater in the field workers at baseline and follow up (41% vs 11% and 41% vs 18% respectively; p = 0.032). The multivariate model for decreased eGFR over three months included

  1. an employee’s status as a field worker,

  2. current smoking,

  3. dehydration, and

  4. pain medication.



As one would expect, the field workers had high levels of metabolic load (> 201 kcal/hr) with the highest effort performed during the period of 6AM to 1PM. During the period of study, the WBGTs were between 31.1 and 32.2 degrees celsius (88 - 90 degrees Fahrenheit); however the maximum WBGTs detected during March and May were 36.2 and 35.4 degrees celsius, respectively (97 and 96 degrees Fahrenheit).

The results confirm that field workers:

  1. spent most of their working hours under heat exposure that exceeded the recommended limits and

  2. had demanding metabolic workloads due to the nature of their labor.



Video 1: Introduction to the Wet Bulb Globe Temperature | Courtesy: The National Weather Service

Field workers expended the most amount of effort in the worst possible heat-related conditions

Despite any imprecision at measurement of hydration status (a marker that is challenging even for seasoned clinicians), the data is relevant to the issue of climate change, but also to the issue of unhealthy working conditions. New efforts should be made at reducing this risk. Climate change *alone* may not explain CKDu in Central America; even players in the FIFA World Cup expose themselves to repeated bouts of strenuous physical activity -- a counter hypothesis proposed by several researchers of CKDu.


These results from the Costa Rican team are thought provoking and parallel the FIFA World Cup, given the dangerous temperatures reached in Qatar during the summer. Moreover, the metabolic demands of footballers -one may argue - could be comparable to that to farm workers. However, we do not see an "epidemic" of CKD amongst the football teams. This disconnect forms the basis of an alternative "toxic hypothesis" for CKDu.

Things to think about as you consider Costa Rica and cast your vote.