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Environmental Chemicals

Sharyle Patton

Sharyle Patton directs the Biomonitoring Resource Center at Commonweal, helping people find out the levels of chemicals in their bodies.
Do you know how many chemicals are in your body? At what levels? Probably not. Every two years, the U.S. Centers for Disease Control and Prevention measures the levels of some environmental chemicals in a group of people that represent the general U.S. population, and publishes its findings in the National Report on Human Exposures to Environmental Chemicals. For most of the chemicals measured, so little research has been done on them that we do not know if the exposures found constitute a health concern. The most recent report (from 2009) confirms widespread exposure to some commonly used industrial chemicals, including many discussed here. Note that this project only tests for a couple of hundred chemicals; over 80,000 chemicals are in use in the U.S., and approximately 1000-2000 new ones are introduced each year. The U.S. government does not require safety testing for new or existing chemicals, and we know very little about how they act in combination with each other. Of critical concern is the ability of chemicals to cross the placenta and influence fetal development (Vandenberg et al. 2009). Alarmingly, 99-100% of the pregnant women in this CDC sample have measurable levels of certain PCBs, organochlorine pesticides, PFCs, phenols, PBDEs, phthalates, polycyclic aromatic hydrocarbons (PAHs) and perchlorate in their bodies (Woodruff et al. 2011).
 
Scientists have long suspected that environmental toxicants could be involved in the development of type 1 diabetes, in part because certain drugs and chemicals could cause diabetes in laboratory animals. They have used these drugs, such as alloxan, streptozotocin (STZ), and cyclophosphamide to induce diabetes in animals for laboratory studies. Some other drugs have also been linked to the development of type 1 diabetes in humans. One example of a chemical inducing insulin-dependent diabetes in humans is the now-banned rat poison Vacor. In the late 1970s, a few people tried to kill themselves by eating Vacor, and ended up with diabetes instead. All of these compounds destroy beta cells, but all act via different mechanisms (Kraine and Tisch 1999; Lenzen 2008). Vacor and STZ both target beta cells, but have also been found linked to type 1-related autoimmunity: Vacor in humans (Karam et al 1980) and STZ in primates (Wei et al 2011). Numerous environmental chemicals can target beta cells (Hectors et al 2011); can they somehow provoke an autoimmune attack? We don't know.
 
Surprisingly, only a very few studies have directly examined the ability of the chemicals we encounter in the environment to affect the development of type 1 diabetes (Howard and Lee 2012). Thus, for many chemicals described here, I also included studies associating them with other types diabetes, or other autoimmune diseases. And, I included information on chemicals and how they can influence other factors that may influence the development of type 1 diabetes, such as increased insulin resistance or weight gain. I have also included information on chemicals that produce effects in the laboratory that could have ramifications for the development of type 1 diabetes, such as by inducing or accelerating autoimmunity, or causing beta cell dysfunction.
 
Sharp (2009) reviews the evidence that environmental toxics may contribute to the development of type 2 diabetes, focusing on Canadian Aboriginal people. Yet this review would be of interest to other communities, and may also be relevant for type 1. He concludes that some toxic chemicals interfere with the functioning of the beta cells, and affect insulin production, and that obesity is also linked to toxics (see the height and weight page). The accepted risk factors for diabetes, including diet, lifestyle, and genetics, do not fully explain the high rates of diabetes in First Nation peoples.

Additional Chemicals

Most chemicals analyzed in relation to diabetes/obesity warrant their own pages, as there are so many studies. A few are just beginning to be studied and do not warrant an entire page. For example, styrene causes higher glucose levels, higher insulin levels, and insulin resistance in rats (Niaz et al. 2017). These effects are similar to type 2 diabetes in humans. Toads exposed to petrol (gasoline) developed high glucose levels after a couple weeks (Isehunwa et al. 2017). People exposed to oil spills have been found to have higher glucose and cholesterol levels (Choi et al. 2017). Another chemical barely researched is hexavalent chromium, a carcinogen and endocrine disruptor made famous in the movie Erin Brockovich. Gestational exposure to hexavalent chromium increased insulin levels and affected glucose uptake and in the offspring of rats (Shobana et al. 2017). This study illustrates that exposure to many chemicals during development is particularly harmful, and I highlight these developmental exposure studies throughout this website.

Other characteristics of how chemicals act may also be important-- and we have not figured them out yet. For example, chemical mixtures may act differently than chemicals individually (Le Magueresse-Battistoni et al. 2017). The timing and dose are also critical to their effects, discussed on the endocrine disruption page. And even the sequence of exposure may play a role-- the effects can differ depending on which exposure occurs first (Ashauer et al. 2017).