Cadmium is….
Much can be said in that blank space. Perhaps most importantly, it should be said that cadmium is serious. It is a highly toxic, highly used industrial chemical that has been strongly associated with the development of lung cancer in humans.
Additionally, it has been more weakly associated with a number of other cancers, including kidney, breast, pancreas and prostate. It is believed to be so potent because of its long half-life (25-30 years)
Cadmium is a natural element found in the earth’s crust, that is flammable, odorless and acutely, as well as chronically, toxic. The greatest concern with cadmium, in addition to its ability to cause disease, is its widespread use. The primary exposure route is inhalation and is usually occupational, via smelting, electroplating, alloy synthesis and fertilizer production, as well as smoking.
It is rated as International Agency for Research on Cancer Group 1, meaning it is definitively carcinogenic in humans. That said, it seems to be a necessary evil in our 21st century world.
Cadmium has been found to lead to chronic obstructive pulmonary disease and pulmonary fibrosis. Local accumulation of cadmium in the lungs via inhalation is thought to be important in the development of eventual lung cancer, though also shorter term lung disease as well, such as pneumonia and emphysema. Immune cell dysregulation has been thought to contribute to cadmium associated lung disease, too.
Some degree of cadmium adaptation is believed to be possible, with acute higher doses of exposure leading to swift cellular death, while adaptation to lower, chronic doses may allow the cell sufficient mutation without cell death to propagate malignant processes.
Ironically, this dual action can help explain both cadmium’s non-neoplastic disease profile, as well as the malignant.
One 2015 meta-analysis of over 20,000 people found a significant correlation between life time lung cancer risk and urinary cadmium levels. Kidneys are particularly vulnerable organs to cadmium, and accumulation over time is a critical issue. Urinary cadmium can be reliably used as a proxy biomarker for long term exposure due to relatively slow clearance. This can be further complicated by renal pathology, or even sub-optimal glomerular filtration rate that accompanies aging.
Since renal disease is the 10th leading cause of death in the United States, it can be assumed that a sizeable portion of any research, or occupational, cohort will have a renal system not suited for healthy cadmium clearance.
As technology advances and research tools follow, differing perspectives on the same problem can be made apparent or reinforced. A 2014 study exposed mice to cadmium oxide nanoparticles. This led to the same sort of lung inflammation seen previously in less refined ways.
OSHA has a permissible exposure limit of 5 micrograms per cubic meter for an eight hour time weighted exposure, for cadmium. NIOSH set a recommended exposure limit for 9 micrograms/cubic meter for a 10 hour workday (for up to a 40 hour workweek). Alternatively, the American Conference of Governmental Industrial Hygienists (ACGIH), set its own threshold value limit on cadmium, both as a respirable fraction (2 micrograms/cubic meter) as well as total particular mixture (10 micrograms/cubic meter).
All this to say the government is trying to keep us safe from cadmium’s risks and we should embrace that!
Cadmium possesses a foundational mechanism of action that allows it to detrimentally impact a variety of human and animal organs. In a context of an abnormally long half life, cadmium is uniquely toxic.
Without proper elimination or substitution measures to control for cadmium use, administrative controls are the most valuable means by which to reduce total exposure by occupationally vulnerable persons. Partnering with government agencies will be key in promoting a fairer and safer world in which we must accept and embrace cadmium’s role.
Dominik Dabrowski is an occupational and environmental medicine physician at HealthPartners and a graduate student at the University of Minnesota’s School of Public Health.
