Kate Applebaum Receives Grant to Investigate Auto Workers’ Kidney Health

Assistant Professor Kate Applebaum has received a four-year, $1.39 million grant from the National Institute for Occupational Safety and Health (NIOSH) to study how auto workers’ exposure to metalworking fluids affects their risk of chronic kidney disease and renal cell carcinoma later in life. The study aims to characterize the health risks faced by millions of workers in the US and worldwide who use metalworking fluids on the job.

“I’m interested in the impact of environmental and occupational exposures on diseases of the kidney because, among other functions, the kidneys provide the critical function of filtering blood, which allows for the excretion of waste products and controlling blood composition,” Applebaum says. This means kidneys are vulnerable to damage, because they take up harmful substances and may metabolize them into more toxic forms to allow for excretion. It also means that having damaged kidneys may compromise individuals’ ability to rid their bodies of waste products.

Preventing chronic kidney disease (CKD) can save healthcare dollars as well as improve quality of life; Applebaum notes that CKD costs account for 20% of Medicare’s budget. CKD affects more than 10% of the US population, and it can progress to end-stage renal disease (ESRD), at which point a patient needs dialysis or a kidney transplant to live. Further, ESRD is associated with a greater risk of renal cell carcinoma (RCC), the most common type of kidney cancer.

Applebaum notes that people may be incurring irreversible damage to their kidneys or even experiencing kidney dysfunction for many years before being diagnosed with chronic kidney disease. This poses a challenge for studying environmental and occupational exposures with kidney outcomes, because disease may be diagnosed much later in time than when a potentially harmful exposure occurred.

A valuable data set

NIOSH funds research into “relevant and high quality scientific investigation that will have an impact in reducing occupational disease and injury,” and data from Applebaum’s research could identify on-the-job exposures whose elimination or reduction could help prevent kidney disease and cancer. Applebaum’s research involves a retrospective cohort study of more than 46,000 auto workers employed at three Michigan plants between 1941 and 1984 and followed through time for diagnosis of or death from chronic diseases or cancer. “Following a large cohort for so many years provides sufficient numbers of cases to allow us to study these relationships,” Applebaum says.

Metalworking fluids are complex mixtures used to cool and coat metal in cutting and grinding operations. The composition of these complex mixtures has changed over time. The data set Applebaum and her colleagues are using has the advantage of including quantitative estimates of workers’ exposure to different types of metalworking fluids over several decades. “This type of data allows us to consider the changing contents in these fluids over time,” explains Applebaum. “For example, some fluids used at certain times may contain higher levels of compounds called polycyclic aromatic hydrocarbons, or PAHs, a potential agent for kidney damage and cancer.”

Complex disease pathways

“Much of epidemiology has historically looked at one exposure and one outcome,” says Applebaum. “Environmental and occupational exposures may lead to more than one chronic disease at the same site. We need to better understand how multiple exposure-related health problems influence each other.” With this study, Applebaum and her colleagues are taking a more complete look at multiple possible adverse outcomes of the kidney. Subjects may develop either ESRD or renal cell carcinoma or both. The study will consider a variety of disease patterns, such as whether someone who developed ESRD following exposure to metalworking fluids might be at greater risk of developing renal cell carcinoma.

One of the goals is to use models that better reflect the complex interplay of exposures leading to multiple adverse events, and how those events influence each other in workers exposed to metalworking fluids. Applebaum’s study will use sophisticated analytic techniques to address these complex disease relationships, with the aim of adding to medical knowledge about how kidney disease progresses and affects the course of other diseases.