Environmental Chemicals

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).

Worldwide, "over 350,000 chemicals and mixtures of chemicals have been registered for production and use, up to three times as many as previously estimated and with substantial differences across countries/regions... the identities of many chemicals remain publicly unknown because they are claimed as confidential (over 50,000) or ambiguously described (up to 70,000)." (Wang et al. 2020). Only about 5% of the chemicals in commerce have even been measured for in people or in the environment; most no one has even looked for (Muir et al. 2023).

There are about 16,000 chemicals known to be in plastic, including some added intentionally and some there unintentionally. We use plastic to wrap our food, and these chemicals can migrate out of the food wrapping into the food (especially if heated-- never microwave or heat plastics!). We know that many of these chemicals can affect our metabolism (Stevens et al. 2024).

Scientists are trying to figure out how to screen these many thousands of chemicals to identify which ones can affect diabetes or obesity. There is progress, although it's a long road. Most regulatory toxicological testing methods so far don't even include tests for diabetes or obesity. Some suggest using "high-throughput screening" methods where you can run thousands of chemicals through a quick screen and identify the ones with potential effects that should be screened further, e.g., in animal studies. The problem is, these methods are not always accurate. But they are getting better! A really extensive analysis of how well high-throughput screening methods identified chemicals that can impact fat cells and metabolism found that the high-throughput methods were pretty accurate, and also that there were a bunch of chemicals that deserve further testing (Filer et al. 2022). Another screening method is being used to screen chemicals for their effects on pancreatic beta cells, which are critical to the development of diabetes (Al-Abdulla et al. 2022).

Environmental Chemicals in U.S. 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.

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). People of color tend to be exposed to higher levels of many chemicals (Nguyen et al. 2020).

Source: Woodruff et al. 2011, EHP.

If you combine environmental chemical exposures with traditional risk factors, you can substantially improve the prediction of diabetes development (Oh et al. 2022).

Reviews of the evidence find that exposure to numerous pollutants may increase the risk of the main types of diabetes as well as obesity (e.g., Khalil et al. 2023).

Type 1 Diabetes

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 chemicals, such as alloxan, streptozotocin (STZ), and cyclophosphamide to induce diabetes in animals for laboratory studies (Algul and Ozcelik, 2025). 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 2018; 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.

Type 2 Diabetes

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.

Do genes play a role? The risk of diabetes and obesity is affected by genetic background. Researchers are trying to figure out if genetic risk affects the role of chemicals in diabetes and obesity. One study from the Netherlands found that genetic risk did not affect the links between chemical and metabolic disease, but both chemicals and genetics were separately linked to the risk of disease (Lu et al. 2024).

Gestational Diabetes

Numerous chemical exposures are linked to gestational diabetes as well (many are reviewed by Eberle and Stichling, 2022 and by Merrill et al. 2023).

Obesity and More

Chemicals are also linked to the risk of other related conditions, such as obesity (see the Height and Weight page) and fatty liver (e.g., see this review focusing on the numerous endocrine disruptors affecting the risk of fatty liver disease in children (e.g., PFAS, plasticizers, pesticides, metals, POPs) (Mosca et al. 2024).

Diabetes Complications

Exposure to environmental chemicals is also linked to an increased risk of complications in people with diabetes (reviewed by He et al. 2024).

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.

Alkylphenol Ethoxylates and Alcohol Ethoxylate Surfactants

These are chemicals found in various consumer products, like household cleaning products. In the lab, they can promote the development of fat cells and the accumulation of triglycerides in fat cells (Kassotis et al. 2018), and increase body weight and triglyceride levels in zebrafish exposed during development (LeFauvre et al. 2023).

Styrene

In humans, a long-term study found that exposure to styrene and ethylbenzene were associated with higher fasting glucose levels (Yu et al. 2023). In laboratory studies, styrene causes higher glucose levels, higher insulin levels, and insulin resistance in rats (Niaz et al. 2017).

Acrolein

The biocide and air pollutant acrolein was associated with insulin resistance in a large U.S. database (NHANES) (Feroe et al. 2016). In China, increased exposure to acrolein was associated with impaired fasting glucose, insulin resistance, and type 2 diabetes, at baseline and at 3 year follow up (Wang et al. 2023). In animals, acrolein causes insulin resistance (Jhuo et al. 2023).

Hexavalent Chromium

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).

Benzo and Methane Chemicals

Exposure to certain benzotriazoles and benzothiazoles, widely-used chemicals, in early pregnancy were associated with impaired glucose tolerance and an increased risk of gestational diabetes in China (Zhou et al. 2019).

Exposure to benzophenone-3 (BP-3), a chemical used in sunscreens, in pregnancy was associated with lower glucose levels and better glucose tolerance in Boston women with fertility problems (Wang et al. 2020). A study from China on this chemical found that childhood exposure was associated with lower body weight (BMI) in boys around puberty (not girls) (Wang et al. 2021). However, another Chinese study found that BP-3 levels were associated with increased risk of insulin resistance, obesity, and abdominal obesity in children (Li et al. 2022). Prenatal exposure to a couple benzophenones were associated with a higher BMI in Chinese children at age 2 (Lv et al. 2024). In Spain, prenatal exposure to BP-3 was associated with higher BMI (non-monotonically) and higher diastolic blood pressure during preadolescence (Güil-Oumrait et al. 2022). In mouse beta cells, benzophenones affected cellular processes in mouse pancreatic beta cells, indicating that exposure could lead to beta cell dysfunction (Szulak et al. 2022).

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), and in fact may be linked to a lower risk (Chen et al. 2024). 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).

Vinyl Chloride

Exposure to vinyl chloride (a chemical released in the East Palestine, Ohio train derailment) caused glucose intolerance in male mice (Zelko et al. 2021). Sometimes it causes metabolic problems in mice fed a high-fat but not low-fat diet (Ge et al. 2023).

MTBE

The gasoline additive MTBE caused glucose intolerance (Saeedi et al. 2017) and lower HDL cholesterol levels and higher VLDL levels in rats (Guo et al 2023). In fish, MTBE and car tire dust affected glucose, triglyceride, and cholesterol levels (Banaee et al. 2023).

Melamine

In Taiwan, melamine exposure was associated with adverse kidney outcomes in people with type 2 diabetes, especially in men, or in those with well controlled blood sugar or good baseline kidney function (Tsai et al. 2023).

6-PPD quinone (6-PPDQ)

This chemical, 6-PPD and 6-PPDQ, used in tires and found in the environment when tires wear, can be toxic to salmon. It also causes high blood glucose levels in nematodes (Liu et al. 2024a). In frogs, it increases cholesterol levels and causes metabolic disruption (Liu et al. 2024b).

Sharyle Patton directs the Biomonitoring Resource Center at Commonweal, helping people find out the levels of chemicals in their bodies.

Mixtures and Other Industrial Chemicals

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) and obesity (Dugandzic et al. 2024).

Mixtures of chemicals, for example, at low doses, affect body weight of rats in the lab (Docea et al. 2018). 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). The complex mixtures of chemicals present in house dust induce biological activity related to fat accumulation in test tubes at levels found in normal houses (Kassotis et al. 2020). The mixtures of endocrine disrupting chemicals found in pregnant women's bodies causes fat deposition in stem cells (Lizunkova et al. 2022). A mixture of PCBs, PFOA, flame retardants, and metals at realistic exposure levels had greater and synergistic obesity-related effects than the individual chemicals alone (Bérubé et al. 2023). Even in sheep, developmental exposure to mixtures of chemicals can contribute to metabolic disease later in life (Ghasemzadeh-Hasankolaei et al. 2023).

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; reviewed by Nagel et al. 2020). 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). This mixture also affect the immune system, including autoimmunity, in adult mice (O'Dell et al. 2021). Toads exposed to petrol (gasoline) developed high glucose levels after a couple weeks (Isehunwa et al. 2017). In Saudi Arabia, workplace exposure in wood, welding, motor mechanic, and oil refinery industries increased the risk of prevalence of prediabetes and type 2 diabetes among the workers, and affected diabetes development (Meo et al. 2020). Certain liquid crystal monomers, used in liquid crystal displays, antagonized peroxisome proliferator-activated receptor gamma (PPARγ), which is involved in obesity (Zhao et al. 2023).

Higher exposure to a UV filter mixture was associated with lower childhood obesity in China, except 2-ethylhexyl-p-methoxycinnamate (EHMC) was associated with higher obesity in girls (Wang et al. 2023). Chemical screening identified another UV filter as a potential obesogen, cinoxate (An et al. 2024).

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).

Climate Change

We don't see much about diabetes and climate change-- yet-- but there are a lot of potential ways that climate change could interact with diabetes. For example, people with diabetes are at higher risk from extreme heat and natural disasters, more susceptible to infections, more susceptible to the effects of air pollution, etc. (see these reviews for example: Al-Shihabi et al. 2023; Ratter-Rieck et al. 2023).

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

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