Phase 1: Recommendations and Findings
Photo Credit: Bonsucro / Joe Woodruff
Phase 1 of the Adelante Initiative was focused on establishing a baseline. This baseline was used to characterize exposures, assess risks and make initial recommendations for improved practices. This baseline will serve as a point of comparison as recommendations are made and implemented throughout the project. The objective being that kidney injury and heat stress events should decrease among the workforce with improved practices.
During Phase 1, four worker categories were selected with similar environmental exposures, but differentiated by observed workload. Workload serves as a proxy for heat stress. Cane cutters were the heaviest workload, followed by seed cutters, then drip irrigation repair workers and finally field support staff, including supervisors and nurses. Biological, qualitative and questionnaire data were collected and analyzed at the beginning and end of the harvest to assess what risk factors emerged for kidney damage and which groups were most at risk. What follows are the key findings from Phase 1, relevant recommendations for producers and researchers, as well as the relevance to other stake holders.
Photo Credit: Bonsucro / Joe Woodruff
Kidney decline appears to be associated with work load
(heaviest workload = most severe decline in kidney function)
Preliminary analysis shows burned cane cutters are 12 times more likely than other jobs to have elevated creatinine (indicator of kidney dysfunction). A lower proportion of seed cutters also have elevated creatinine at the end of harvest. This is consistent with the hypothesis that heat stress is a main driver of CKDu progression and potentially a main cause.
The current efforts at San Antonio Sugar Mill to reduce heat stress among the sugarcane workforce appear to be insufficient to prevent incident kidney injury (IKI) among cane cutters and to a lesser extent among the seed cutters. However, kidney injury was nearly absent in other workload categories that previously experienced declines in kidney function suggesting that the intervention that was implemented was sufficient for lower workloads.
Incident kidney injury increased with increasing heat stress according to job categories of field workers. Despite considerable improvements in working conditions, the job categories with highest heat stress still present kidney injury at an elevated rate (27% of burned cane cutters, 8% of seed cutters, 2.3% of drip irrigation repair workers and 1.9% field support workers). The risk of kidney injury was 14 times higher for cane cutters than for field support staff, and the risk for seed cutters was 4 times higher.
There was evidence for inflammation being part of the causal pathway
Cane cutters with kidney injury reported significantly more symptoms of fever, weakness and headache than cane cutters without, which is compatible with higher heat stress or an inflammatory response. Fever was associated with high levels of C-reactive protein (CRP) which is indicative of inflammation and previously indicated as related to heat stress in studies by the U.S. military. Of note, “fever” can occur due to both infection and heat stress. The current hypothesis among the Adelante Initiative research team is that reported fever is related to heat stress events primarily associated with workload as there is no plausible hypothesis as to why fever would be so much more common among the field laborer than the field support staff who work in the same field environment and have similar social economic positions.
There were no significant differences of CRP levels at start of harvest between job categories. At end of harvest, high CRP levels were more frequent, particularly among cane cutters, and in general, among any workers with kidney injury and a decline in kidney function.
Young men more likely to have significant decline in kidney function
Young men are the most at risk of kidney dysfunction, which is the opposite trend seen in the general population where older people generally have lower kidney function. At San Antonio Sugar Mill only men work as cane cutters. Among seed cutters, kidney injury occurrence was similar among woman and men.
Affected workers are more likely to leave employment (loss-to-follow-up) so findings are likely to be an underestimate
Workers at Ingenio San Antonio are rightly evaluated for kidney function, and those that have compromised function and do not recover after a set amount of time are released from the workforce. Workers may also self-select out of the workforce once their kidney function becomes compromised. This leads to what is known as the “Healthy Worker Effect”. This means that there will be a preponderance of healthy workers remaining in the workforce at the end of a harvest and there is a tendency for sick workers to make up a significant portion of those who have left the workforce.
A lower kidney function pre-harvest is associated with decline in kidney function over the harvest.
Baseline kidney function was associated with kidney injury and declined kidney function during or at end of harvest. Those with highest creatinine at pre-harvest were at the highest risk of kidney decline over the harvest.
The mill’s creatinine level cut-off of 1.3 mg/dl for hiring male workers was too high. It has since been addressed and a more specific measure using age and creatinine levels ensures only healthy workers enter the workforce. Those with a creatinine near 1.3 mg/dl already have impaired kidney function. Those with impaired function are more likely to have greater damage done in adverse conditions.