Unhealthy diet and lack of exercise are the main factors that contribute to weight gain and obesity, but studies have found that obesogens may also be playing a role. Obesogens do not directly cause obesity, but they may increase the sensitivity, or susceptibility, to gaining weight, especially when the exposures occur during development.

Obesogens are believed to work in several ways.

They may change how a person’s fat cells develop, meaning they may increase fat storage capacity or the number of fat cells.

Also, obesogens may make it more difficult to maintain a healthy weight, by changing how the body regulates feelings of hunger and fullness, or increasing the effects of high fat and high sugar diets.

Examples of chemicals that may be obesogens

• Cigarette smoke
• Air pollution
• Tributyltin, a chemical that is widely used as a fungicide and heat stabilizer in polyvinyl chloride (PVC) piping
• Flame retardants
• Phthalates, a broad class of chemicals that are added to many consumer products to make them softer
• Bisphenol A
• Some pesticides
• Polychlorinated biphenyls (PCBs), industrial chemicals that were used widely in the past in products such as paints, cements, fluorescent light ballasts, sealants, and adhesives.

Health consequences

The most sensitive time for exposure to obesogens is during early development — as a fetus or during the first years of life — when the body’s weight control mechanisms are being developed.

Obesity is a disease itself, but other diseases or disorders that develop as a result of, or in combination with obesity, such as cardiovascular disease, liver disease, diabetes, arthritis, and others, also can contribute to health problems associated with weight gain.

Prevention

Try to minimize exposures to environmental chemicals. This is often challenging, since it is hard to know where and what products contain these chemicals.

Some general advice is to:

• Eat fresh fruit and vegetables
• Reduce use of plastics
• Do not use plastics in the microwave
• Purchase furniture that has not been treated with flame retardants
• Choose fragrance-free products

Air pollution is a familiar environmental health hazard. We know what we’re looking at when brown haze settles over a city, exhaust billows across a busy highway, or a plume rises from a smokestack. Some air pollution is not seen, but its pungent smell alerts you.

When the National Ambient Air Quality Standards were established in 1970, air pollution was regarded primarily as a threat to respiratory health. Over the next decades as air pollution research advanced, public health concern broadened to include cardiovascular disease; diabetes mellitus; obesity; and reproductive, neurological, and immune system disorders.

Air pollution exposure is associated with oxidative stress and inflammation in human cells, which may lay a foundation for chronic diseases and cancer. In 2013, the International Agency for Research on Cancer of the World Health Organization (WHO) classified air pollution as a human carcinogen.

What Is Air Pollution?

Air pollution is a mix of hazardous substances from both human-made and natural sources.

Vehicle emissions, fuel oils and natural gas to heat homes, by-products of manufacturing and power generation, particularly coal-fueled power plants, and fumes from chemical production are the primary sources of human-made air pollution.

Nature releases hazardous substances into the air, such as smoke from wildfires, which are often caused by people; ash and gases from volcanic eruptions; and gases, like methane, which are emitted from decomposing organic matter in soils.

Traffic-Related Air Pollution (TRAP), from motor vehicle emissions, may be the most recognizable form of air pollution. It contains most of the elements of human-made air pollution: ground-level ozone, various forms of carbon, nitrogen oxides, sulfur oxides, volatile organic compounds, polycyclic aromatic hydrocarbons, and fine particulate matter.

Ozone, an atmospheric gas, is often called smog when at ground level. It is created when pollutants emitted by cars, power plants, industrial boilers, refineries, and other sources chemically react in the presence of sunlight.

Noxious gases, which include carbon dioxide, carbon monoxide, nitrogen oxides (NOx), and sulfur oxides (SOx), are components of motor vehicle emissions and byproducts of industrial processes.

Particulate matter (PM) is composed of chemicals such as sulfates, nitrates, carbon, or mineral dusts. Vehicle and industrial emissions from fossil fuel combustion, cigarette smoke, and burning organic matter, such as wildfires, all contain PM.

A subset of PM, fine particulate matter (PM 2.5) is 30 times thinner than a human hair. It can be inhaled deeply into lung tissue and contribute to serious health problems. PM 2.5 accounts for most health effects due to air pollution in the U.S.

Volatile organic compounds (VOC) vaporize at or near room temperature—hence, the designation volatile. They are called organic because they contain carbon. VOCs are given off by paints, cleaning supplies, pesticides, some furnishings, and even craft materials like glue. Gasoline and natural gas are major sources of VOCs, which are released during combustion.

Polycyclic aromatic hydrocarbons (PAH) are organic compounds containing carbon and hydrogen. Of more than 100 PAHs known to be widespread in the environment, 15 are listed in the Report on Carcinogens. In addition to combustion, many industrial processes, such as iron, steel, and rubber product manufacturing, as well as power generation, also produce PAHs as a by-product. PAHs are also found in particulate matter.

How does air pollution affect our health?

Respiratory Disease

• Air pollution can affect lung development and is implicated in the development of emphysema, asthma, and other respiratory diseases, such as chronic obstructive pulmonary disease (COPD).
• PM and nitrogen oxide are linked to chronic bronchitis.
• In 2020, a major public health challenge was confluence of the COVID-19 pandemic and wildfires across the western U.S. Building on a well-established connection between air pollution and respiratory-tract infections, a study linked wildfire smoke with additional COVID-19 cases and deaths.

Cardiovascular Disease

• Fine particulate matter can impair blood vessel function and speed up calcification in arteries.
• NIEHS researchers established links between short-term daily exposure by post-menopausal women to nitrogen oxides and increased risk of hemorrhagic stroke.
• For a cross-section of older Americans, exposure to TRAP can result in lowered levels of high-density lipoprotein, sometimes called good cholesterol, increasing their risk for cardiovascular disease.
• According to a National Toxicology Program (NTP) report, TRAP exposure also increases a pregnant woman’s risk for dangerous changes in blood pressure, known as hypertensive disorders, which are a leading cause of pre-term birth, low birth weight, and maternal and fetal illness and death.

Cancer

• A large study of more than 57,000 women found living near major roadways may increase a woman’s risk for breast cancer.
• The NIEHS Sister Study found other airborne toxic substances, especially methylene chloride, which is used in aerosol products and paint removers, are also associated with increased risk of breast cancer.
• Occupational exposure to benzene, an industrial chemical and component of gasoline, can cause leukemia and is associated with non-Hodgkin’s Lymphoma.
• A long-term study, 2000-2016, found an association between lung cancer incidence and increased reliance on coal for energy generation.

Whom does air pollution affect the most?

Air pollution affects everyone’s health, but certain groups may be harmed more.
Almost 9 out of 10 people who live in urban areas worldwide are affected by air pollution.

Children

The NIEHS-funded Children’s Health Study at the University of Southern California is one of the largest studies of the long-term effects of air pollution on children’s respiratory health. Among its findings:

• Higher air pollution levels increase short-term respiratory infections, which lead to more school absences.
• Children who play several outdoor sports and live in high ozone communities are more likely to develop asthma.
• Children living near busy roads are at increased risk for asthma.
• Children with asthma who were exposed to high levels of air pollutants were more likely to develop bronchitis symptoms.
• Living in communities with higher pollution levels can cause lung damage.

Other studies on women and children

• NIEHS-funded researchers from the University of California, Davis, Environmental Health Sciences Center are conducting the Bio-Specimen and Fire Effects (B-SAFE) Study. This ongoing project seeks to discover if and how recent wildfires and their smoke affected pregnant women and their babies. Begun in 2017, study participants are pregnant women who were living in Northern California when the 2018, 2019, or 2020 wildfires occurred there.
• Breathing PM 2.5, even at relatively low levels, may alter the size of a child's developing brain, which may ultimately increase the risk for cognitive and emotional problems later in adolescence.
• Prenatal exposure to PAHs was associated with brain development effects, slower processing speed, attention-deficit and hyperactivity disorder (ADHD) symptoms, and other neurobehavioral problems in urban youth.
• In New York City, prenatal exposure to air pollution may play a role in childhood ADHD-related behavior problems.
• Prenatal exposure to particulate matter was associated with low birth weight.
• Women exposed to high levels of fine particulate matter during pregnancy, particularly in the third trimester, may have up to twice the risk of having a child with autism.
• Second and third trimester exposure to PM 2.5 might increase the chance of those children having high blood pressure in early life.
• In California’s agricultural San Joaquin Valley, women who were exposed to high levels of carbon monoxide, nitrogen oxide, or nitrogen dioxide during their first 8 weeks of pregnancy were more likely to have a baby with neural tube defects.
• In Marietta, Ohio, home to a ferromanganese refinery, manganese concentrations in blood and hair, a biomarker of air pollution exposure, were associated with lower child IQ scores.

Older adults

• Alzheimer’s disease and related dementias are a public health challenge for aging populations. NIEHS-funded researchers at the University of Washington identified a link between air pollution and dementias. This well-conducted study adds considerable evidence that ambient air fine particles increase risk of dementias.
• Air pollution was linked to a greater chance of developing several neurological disorders, including Parkinson's disease, Alzheimer's disease, and other dementias. Hospital admissions data from 63 million older adults in the U.S., obtained over 17 years (2000-2016), was analyzed along with estimated PM 2.5 concentrations by zip code to conduct the study.
• In older adults, long-term exposure to TRAP may significantly hasten physical disabilities. The risk is more pronounced among racial minorities and lower-income people.
• PM 2.5 air pollution is also associated with accelerated memory problems and Alzheimer’s-like brain declines, which was seen among women 65 years of age and older.
• Nutrients may counter some harmful effects from air pollution. A 2020 study found omega-3 fatty acids, obtained by eating certain fish, may protect against PM 2.5-associated brain shrinkage in older women.

Rural dwellers

• An NIEHS-funded study found that concentrations of PM 2.5 in rural Washington State were comparable to urban Seattle. In this study, as regional PM 2.5 increased, there were increased asthma symptoms, such as limitation of activities, more wheezing, and more nighttime waking, in rural children.
• In the rural U.S., large-scale animal feeding operations might compromise regional air quality through emission of pollutants, such as ammonia gas. A study found acute lung function problems in children with asthma in such areas.

Cardiovascular disease is a general term used to describe conditions affecting the health of the heart or blood vessels. Many of the health problems associated with heart disease are related to atherosclerosis or the buildup of plaque in the walls of the arteries. For those with heart disease, the buildup can result in blood clots, which can block the flow of blood and lead to a heart attack or stroke.   

The disease is the leading cause of death in the United State with most of the deaths occurring in people over 65 years of age. One in three Americans has heart or blood vessel disease.

Traditional risk factors for cardiovascular disease are: male sex, older age, increased blood pressure, high total cholesterol, low HDL (high density lipoprotein) and smoking. In addition, other risk factors, such as diabetes and air pollution exposure, have been found to contribute to the development of cardiovascular disease.  

A large body of science has shown that air pollution can exacerbate existing cardiovascular disease and contribute to the development of the disease. The evidence is particularly strong for outdoor particle pollution exposure. Fine particulate matter (particulate matter with diameters less than 2.5 µm or PM2.5) can increase the risk of cardiovascular events.

Research by EPA and others has found that exposure to increased concentrations of PM2.5 over a few hours to weeks can trigger cardiovascular disease-related heart attacks and death. Longer-term exposure can lead to increased risk of cardiovascular mortality and decreases in life expectancy.

For the individual, the risk of cardiovascular disease from particle pollution is smaller than the risk from many other well-established risk factors that are described above. For the population as a whole, however, short -and long-term exposure has been shown to increase hospitalizations for serious cardiovascular events such as coronary syndrome, arrhythmia, heart failure, stroke, and sudden cardiac death, particularly in people with established heart disease.

People with chronic heart disease may experience one or more of the following symptoms following exposure to fine particulate matter:

• Heart palpitations
• Unusual fatigue
• Lightheadedness
• Shortness of breath
• Chest tightness or pain in the chest, neck or shoulder

What is PM2.5?

PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

Particle pollution includes:

• PM10 : inhalable particles, with diameters that are generally 10 micrometers and smaller; and
• PM2.5 : fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.
  • How small is 2.5 micrometers? Think about a single hair from your head. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle.

Sources of PM2.5:

• These particles come in many sizes and shapes and can be made up of hundreds of different chemicals.
• Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks, or fires.
• Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries, and automobiles.
• For more information about particle pollution, visit https://www.epa.gov/pm-pollution/particulate-matter-pm-basics.
• For more information about particulate matter and cardiovascular health visit: https://www.epa.gov/pmcourse/particle-pollution-and-cardiovascular-effects

Where and When is Particle Pollution a Problem?

Sources of fine particle pollution include power plants, factories, automobiles, and wildfire smoke. These tiny particles can be found year-round and contribute to air quality problems in many major cities and other areas of the United States.

Some particles can remain in the atmosphere for days to weeks. Consequently, particle pollution generated in one area can travel hundreds or thousands of miles and influence the air quality of regions far from the original source.  

Research has determined that particle pollution levels can be especially high in the following circumstances:

• Near busy roads, in urban areas (especially during rush hour), and in industrial areas.
• When there is smoke in the air from wood stoves, fireplaces, campfires, wildfires, or prescribed burns. 
• When the weather is calm, allowing air pollution to build up. For example, hot humid days with stagnant air have much higher particle concentrations than days with air partially “scrubbed” by rain or snow.

Because of their small size, fine particles outdoors can penetrate into homes and buildings. Therefore, high outdoor particle pollution levels can elevate indoor particle pollution concentrations. 

Who is at increased risk of PM2.5 exposure?

Scientific evidence indicates that some populations may be at increased risk of PM2.5-related health effects, which may include clinical cardiovascular outcomes. These include:

• People with underlying cardiovascular conditions (e.g., ischemic heart disease, heart failure) or who previously experienced cardiovascular events (e.g., myocardial infarction, stroke)
• People with diabetes
• People with elevated cholesterol levels
• Non-white populations
• People who are obese
• People of low socioeconomic status
• Older adults

People Who Live in Areas With Air Pollution— While the United States has experienced improved air quality and reductions in PM2.5, there are still many people who are exposed to high levels of the pollutant because of where they live and/or their vulnerability due to their health conditions. Individuals who live or work near roadways, railyards, seaports, or industrial areas may be exposed to higher levels of PM2.5.

People Exposed to Smoke from Wildland Fires— Smoke from wildland fires, which includes wildfires and prescribed fires, consists of  a complex mixture of pollutants, including PM2.5, which is a main component of smoke. Studies have shown that wildland fire smoke exposure can lead to a variety of health effects, especially for those with pre-existing lung and heart conditions.

People Who Smoke Tobacco Products Or Are Exposed to Secondhand Smoke— Smoking tobacco products is a main cause of lung cancer, heart disease and stroke, among other diseases. In addition, the health effects of secondhand smoke on nonsmoking adults and children are harmful and numerous. Secondhand smoke causes cardiovascular disease (heart disease and stroke), lung cancer, sudden infant death syndrome, more frequent and severe asthma attacks, and other serious health problems.

Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics. It is found in various products including shatterproof windows, eyewear, water bottles, and epoxy resins that coat some metal food cans, bottle tops, and water supply pipes.

How does BPA get into the body?

The primary source of exposure to BPA for most people is through the diet. While air, dust, and water are other possible sources of exposure, BPA in food and beverages accounts for the majority of daily human exposure.

Bisphenol A can leach into food from the protective internal epoxy resin coatings of canned foods and from consumer products such as polycarbonate tableware, food storage containers, water bottles, and baby bottles. The degree to which BPA leaches from polycarbonate bottles into liquid may depend more on the temperature of the liquid or bottle, than the age of the container. BPA can also be found in breast milk.

Why are people concerned about BPA?

One reason people may be concerned about BPA is because human exposure to BPA is widespread. The 2003-2004 National Health and Nutrition Examination Survey (NHANES III) conducted by the Centers for Disease Control and Prevention (CDC) found detectable levels of BPA in 93% of 2517 urine samples from people six years and older. The CDC NHANES data are considered representative of exposures in the United States. Another reason for concern, especially for parents, may be because some animal studies report effects in fetuses and newborns exposed to BPA.

If I am concerned, what can I do to prevent exposure to BPA?

Some animal studies suggest that infants and children may be the most vulnerable to the effects of BPA. Parents and caregivers can make the personal choice to reduce exposures of their infants and children to BPA:

• Don’t microwave polycarbonate plastic food containers. Polycarbonate is strong and durable, but over time it may break down from over use at high temperatures.
• Plastic containers have recycle codes on the bottom. Some, but not all, plastics that are marked with recycle codes 3 or 7 may be made with BPA.
• Reduce your use of canned foods.
• When possible, opt for glass, porcelain or stainless steel containers, particularly for hot food or liquids.
• Use baby bottles that are BPA free.

What are flame retardants?

Flame retardants are chemicals that are added or applied to materials in order to slow or prevent the start/growth of fire. They have been used in many consumer and industrial products since the 1970s, to decrease the ability of materials to ignite.

Flame retardants are often added or applied to the following products.

• Furnishings, such as foam, upholstery, mattresses, carpets, curtains, and fabric blinds.
• Electronics and electrical devices, such as computers, laptops, phones, televisions, and household appliances, plus wires and cables.
• Building and construction materials, including electrical wires and cables, and insulation materials, such as polystyrene and polyurethane insulation foams.
• Transportation products, such as seats, seat covers and fillings, bumpers, overhead compartments, and other parts of automobiles, airplanes, and trains.

Many flame retardants have been removed from the market or are no longer produced. However, because they do not easily break down, they can remain persistent in the environment for years. They can also bioaccumulate, or build up in people and animals over time.

How are people exposed to flame retardants?

People can be exposed to flame retardants through a variety of ways, including diet; consumer products in the home, car, airplane, and workplace; and house dust.

• These chemicals can get into the air, water, and soil during manufacture.
• Chemicals can leak from products into dust and into the air.
• Dust can get on hands and food and then into the mouth when food is eaten.
• Through e-waste or the uncontrolled burning and dismantling of electronic and electric waste.

What can be done to reduce exposure to flame retardants?

• Keep dust levels down, by wet mopping and vacuuming with a high efficiency particulate air (HEPA) filter to help remove contaminants from your home.
• Wash your hands and those of your children often. Hand-to-mouth contact exposes people to flame retardants.
• When purchasing new products, try to purchase baby products and furniture filled with cotton, polyester, or wool, instead of polyurethane foam.
• Reduce dust by having a good ventilation system in your home.

What are some of the potential health effects associated with flame retardants?

Although flame retardants can offer benefits when they are added to some products, a growing body of evidence shows that many of these chemicals are associated with adverse health effects in animals and humans. These include:

• Endocrine and thyroid disruption
• Impacts to the immune system
• Reproductive toxicity
• Cancer
• Adverse effects on fetal and child development
• Neurologic function

Who is most vulnerable?

Children may be particularly vulnerable to the toxic effects of these chemicals, because their brain and other organs are still developing. Hand-to-mouth behavior and proximity to the floor increases the potential of children to be exposed to flame retardants. Researchers have found that children have higher concentrations of flame retardants in their bodies than adults.

Are there different types of flame retardants?

There are hundreds of different flame retardants. They are often broken into categories based on chemical structure and properties. In general, flame retardants are grouped based on whether they contain bromine, chlorine, phosphorus, nitrogen, metals, or boron.

Brominated flame retardants — Contain bromine and are the most abundantly used flame retardants. Used in many consumer goods, including electronics, furniture, building materials, etc. and have been linked to endocrine disruption among other effects.

Polybrominated diphenyl ethers (PBDE’s) —PBDEs do not chemically bind with the products to which they are added (furniture, electronics, etc.) so they easily release from these products and enter air and dust. PBDEs can lower birth weight/length of children, and impair neurological development.

Tetrabromobisphenol A (TBBPA) — Widely used to make computer circuit boards and electronics. Also used in some textiles and paper, or as an additive in other flame retardants.

Hexabromocyclododecane (HBCD) — An additive primarily used in polystyrene foam building materials. The primary risk to humans is from leaching out of products and getting into indoor dust. Low levels of HBCD have also been found in some food products.

Organophosphate flame retardants (OPFRs) — With the phasing out of PBDEs, some OPFRs have been identified as replacements.

NIEHS-supported researchers are also looking at the health effects of newer flame retardant alternatives that are being brought to market.

Microplastics are everywhere. They can even be found in our bodies. These extremely small pieces of plastic debris in the environment result from the disposal and breakdown of consumer products and industrial waste.

And now, according to a study funded by NIEHS, human exposure to microplastics and plastic additives - chemicals such as heat and UV stabilizers, plasticizers, and flame retardants added to improve certain properties of plastics - may be linked to an increased risk for obesity by affecting metabolism and promoting the growth of fat cells.

The scientists theorize relationships among the global increase of plastics production, human exposure to microplastics, and the global increase of overweight and obesity in populations.

"Plastics production and usage has grown considerably over the past five decades," said Kurunthachalam Kannan, Ph.D., lead author and professor in the Department of Pediatrics at the New York University Grossman School of Medicine. "This coincides with the rise in overweight and obesity rates in a global context. While there are several factors, including a lack of physical activity, to consider in the obesity pandemic, there is evidence that caloric intake has not significantly changed in the last decades, leading to the conclusion that plastics can be playing a significant role."

The Pervasive Nature of Microplastics

Plastic waste has increased exponentially in the previous decades. Through weathering, a process including erosion, abrasion, oxidation, and decomposition, these plastics break down in the environment into microplastics - any plastic particles smaller than 5 millimeters in size.

The publication cites that in the European Union alone, an estimated 75,000 - 300,000 tons of microplastics are created each year. Further, estimates suggest that microplastics could make up 13.2% of the total weight of plastics in the world by 2060. Degradation of larger plastics are the source of most common microplastics. Additional types of microplastics come from microfibers or synthetic textiles, plastic fragments and pellets, as well as microbeads used in cleaning and cosmetic products.

"Microplastic exposure in people is ubiquitous," said Kannan. "Almost everybody is exposed to microplastics on a daily basis, and therefore, it is a global public health problem."

Microplastics and plastic additives get released into the environment, including oceans, surface water and wastewater, sediment, and indoor and outdoor air. Humans are exposed to microplastics daily through several pathways, including inhalation of indoor and outdoor air and dust, and ingestion of contaminated food and water.

"An average person is exposed to a few to several milligrams of microplastics daily," said Kannan. "When you compare this exposure to other environmental chemicals, which is usually in nanograms or micrograms daily, microplastics exposure is huge, and it is a cause for concern."

The publication cites that based on the current information, the most common sources of microplastics exposure are inhaled indoor air and dust, drinking water and packaged beverages, contaminated foods, and cosmetics and textiles. Notably, plastic-bottled water consumption is currently the second-greatest source of exposure to microplastics globally, according to the publication.

Microplastic contamination in seafood and sea salt has been known however, additional exposures from other foods and plastic food packaging have not been studied. The authors note that one of its limitations is quantifying microplastics exposures in food due to a lack of standard and validated analytical methods.

Health Effects of Exposure to Microplastics

The persistent exposure to microplastics and plastic additives raises significant health concerns. While most microplastics are excreted through feces, particles smaller than 150 micrometers can cross into the intestinal epithelium. Particles under 20 micrometers can reach organs, such as the lungs and liver, through systemic circulation. Further, inhalation exposure can lead to direct deposition of microplastic particles in lungs. Microplastics that are between 0.1 and 10 micrometers can even cross the blood-brain barrier and the placenta.

While the health risks of microplastics in humans are not fully understood, laboratory animal and cell culture studies suggest that these chemicals can encourage obesity through several mechanisms.

Microplastics fewer than 20 micrometers that penetrate the cell membrane can cause an immune response and potentially cell damage. Microplastics induce oxidative stress and alter energy and fatty acid metabolism. Accumulation of microplastics in the liver and kidney has also been shown to boost the growth and accumulation of fat cells and disrupt energy balance, which ultimately can affect body weight.

In addition, plastic additives can contain harmful chemicals , which can act as co-contaminants in microplastics. Many of these plastic additives, including organotins, phthalates, bisphenols, and toxic metals, affect fat cell growth as well as the proteins that regulate lipid and glucose metabolism. Bisphenol A (BPA), commonly used to make certain types of plastics, is known to affect the endocrine system and the body's hormonal balance, which can impact metabolism and weight gain.

Overweight and obesity are a growing concern worldwide as they increase the risks of health issues, such as diabetes, cardiovascular disease, hypertension, and certain types of cancer. The World Health Organization estimates that obesity has nearly tripled since 1975. While obesity has increased, so has exposure to microplastics and plastic additives, suggesting an association between the two.

Kannan says there is more to learn about the toxic effects of microplastics in humans, and how specific factors, such as type, size, and concentrations of microplastics affect the metabolic pathways that could lead to increased body weight gain.

"The first major knowledge gap is in understanding the magnitude of exposure," said Kannan. "There is still a lot to be done in understanding the sources and pathways of exposure to microplastics; for instance, exposure doses through food and food-packaging are still not fully known. We need to develop methods to quantify the exposures comprehensively and holistically."

An electronic cigarette, or e-cigarette, is a handheld electronic device that simulates the feeling of traditional tobacco smoking. Devices can resemble traditional cigarettes, cigars, or pipes, or items like pens or USB sticks. They work by heating a liquid, which typically contains nicotine, to generate an aerosol or vapor that users inhale. Vaping is the commonly used term for the use of e-cigarettes.

Vaping has gained popularity, both in the U.S. and worldwide, particularly among teens and young adults, due to easy availability, targeted marketing, and creative e-liquid flavors. While e-cigarettes are often thought to be safer than tobacco cigarettes, little is known regarding the health effects of their use. Scientists at NIEHS are conducting the E-Cigs and Smoking Study, to develop new biomarkers, or measurable indicators of a normal or abnormal process or condition or disease, of tobacco smoke exposure or e-cigarette use.

The term “obesogen” describes a chemical that promotes excessive weight gain by increasing adipocyte (fat cell) size or number, changing metabolism to favor fat storage, or altering the control of appetite and satiety. Previous studies have suggested that prenatal exposure to obesogens can alter metabolism in mice and predispose multipotent mesenchymal stem cells (MSCs) to become fat cells, but whether these changes last through subsequent generations was unknown. A team of researchers investigating this question exposed pregnant mice to tributyltin (TBT) and found impacts on adipogenesis through the third generation [EHP 121(3):359–366; Chamorro-Garcia et al.].

TBT, which has been used as a biocide in marine paints and in textile products such as carpets, is a persistent organic pollutant that is ubiquitous in the environment. Exposure to TBT is thought to occur through many sources, including food, house dust, and consumer products.

In the current study, male offspring (i.e., the F1 generation) of mice exposed to TBT during pregnancy showed marked increases in the number and size of white fat cells and significant but less pronounced increases in the weight of white fat deposits (or “depots”) around the kidney and under the skin. The two subsequent generations (F2 and F3) also showed increases in fat cell size and number and, at the two higher TBT doses, in fat depot weight. Females showed more modest differences following TBT prenatal exposure, including both increases and decreases in cell numbers, depending on location.