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Environmental Chemicals

Environmental Chemicals in U.S. Pregnant Women

chemicals in pregnant women

The number of chemicals detected in U.S. pregnant women out of 52 tested for, in 2003–2004. Each vertical bar represents one woman. Exposure is ubiquitous.
Do you know how many chemicals are in your body? At what levels? Probably not. I certainly don't. 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 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, PFASs, phenols, PBDEs, phthalates, polycyclic aromatic hydrocarbons (PAHs) and perchlorate in their bodies (Woodruff et al. 2011).
 
Scientists have long suspected that environmental chemicals 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 (Bodin et al. 2015; Howard 2019; Howard 2018Howard 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.
 
There is a ton of evidence that environmental chemicals may contribute to the development of type 2 diabetes, reviewed throughout this website. Sharp (2009), for example, focuses on Canadian Aboriginal people. Yet his 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, as well as obesity (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

Sharyle Patton

Sharyle Patton directs the Biomonitoring Resource Center at Commonweal, helping people find out the levels of chemicals in their bodies.
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. In human studies, for example, men who work in the plastic industry have a higher risk of type 2 diabetes and pre-diabetes, and the longer they have worked there, the higher the risk (Meo et al. 2018). People exposed to oil spills have been found to have higher glucose and cholesterol levels (Choi et al. 2017), while the chemicals found in fracking wastewater cause effects linked to weight gain in cells at levels that humans are exposed to (Kassotis et al. 2018). Some of these authors further found that developmental exposure to a mixture of 23 unconventional oil and gas chemicals altered energy expenditure and spontaneous activity in adult female mice, although it had no effects on glucose tolerance or body weight/composition (Balise et al. 2019a). However, a further study by the same authors found that when the mice were allowed to age, and had a short 3-day exposure to a high-fat, high-sugar diet, they developed increased body weight and higher fasting blood glucose levels (Balise et al. 2019b).

In other laboratory studies, styrene causes higher glucose levels, higher insulin levels, and insulin resistance in rats (Niaz et al. 2017). Toads exposed to petrol (gasoline) developed high glucose levels after a couple weeks (Isehunwa et al. 2017). Another chemical barely researched is hexavalent chromium, a carcinogen and endocrine disruptor made famous in the movie Erin Brockovich.

Some studies have found that trihalomethanes, which are by-products of water chlorination (found in pools or drinking water), are not associated with increased rates of type 2 diabetes (Gängler et al. 2019), or with pre-diabetes (Ioannou et al. 2019). However, a different study found a possible link, and laboratory studies show that these chemicals might be linked to insulin resistance (Makris et al. 2016).

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.

Exposure during pregnancy may be important for the woman (as well as the fetus), and contribute to gestational diabetes (Varshavsky et al. 2019). For example, higher paraben levels are associated with higher glucose levels in pregnant women (Bellavia et al. 2018), with gestational diabetes in overweight/obese pregnant women (Li et al. 2018), and with lower blood pressure in pregnant women (Warembourg et al. 2018. But it also depends on the type of paraben; in Chinese women, ethylparaben levels were positively associated with gestational diabetes, but not methyl paraben or propylparaben (Liu et al. 2019). The use of personal care products (which often contain parabens or other chemicals) is also linked to higher blood glucose levels in pregnancy (Bellavia et al. 2019). These pages discuss further associations between chemical exposures and gestational diabetes. Prenatal exposure to parabens may also affect the growth of the fetus and child (Wu et al. 2018). Parabens are also associated with obesity (Kolatorova et al. 2018).

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), and these mixtures are linked to metabolic diseases such as diabetes (Le Magueresse-Battistoni et al. 2018). Mixtures of chemicals, for example, at low doses, affect body weight of rats in the lab (Docea et al. 2018). The timing and dose are also critical to their effects, discussed on the Endocrine Disruption page. Mixtures of chemicals found in the environment, like raw sewage entering wastewater treatment plants, can cause fat accumulation in laboratory experiments (Barbosa et al. 2019).

Another issue that most studies do not address is that even the sequence of exposure may play a role-- the effects of chemicals can differ depending on which exposure occurs first (Ashauer et al. 2017).

Additional substances with endocrine disrupting effects may also be linked to diabetes, including engineered nanomaterials/nanoparticles (Ali 2019Mao et al. 2019Priyam et al. 2018).

References

For studies on specific chemicals, see the link on the bottom of each subpage. To see overall lists of studies of environmental chemicals and various types of diabetes/obesity, see these PubMed collections:

All environmental chemicals and diabetes/obesity (includes type 2, type 1, and gestational diabetes; insulin resistance; obesity/body size)
All chemicals and obesity and metabolic syndrome (includes studies on growth, height, weight, obesity, insulin resistance, lipids, and adipose (fatty) tissue)
All chemicals and type 1 diabetes
All chemicals and gestational diabetes
All chemicals and diabetes complications and blood glucose control