Our environment affects our health. If parts of the environment, like the air, water, or soil become polluted, it can lead to health problems. For example, asthma pollutants and chemicals in the air or in the home can trigger asthma attacks.

Some environmental risks are a part of the natural world, like radon in the soil. Others are the result of human activities, like lead poisoning from paint, or exposure to asbestos or mercury from mining or industrial use.

Children and infants are especially vulnerable to pollution and other environmental factors that may cause serious health problems. There are several reasons why children are at higher risk:

• Pound for pound, children eat, drink, and breathe more than adults relative to their size.
• Children frequently put objects in their mouths, explore more, and play on the floor and ground.
• Protective bodily systems, such as those that filter pollutants from inhaled air and process chemicals in the body, are not yet fully functional in children.
• During periods of rapid growth and development in childhood, normal biological processes may be disrupted by environmental chemicals.

Doctors and scientist do not always know what causes a disease or a disorder. Some health conditions are genetic and can be passed from grandparents to parents to children. Some health problems may be caused by injury from things in our environment. Most scientists agree that diseases are probably caused by both, which is called the gene-environment interaction. Since we cannot do much to change our genes, researchers believe that identifying and managing environmental hazards offers the best hope for prevention.

By protecting children, we may also improve their health as adults. According to NIEHS research, when pregnant women improved their nutrition and reduced exposure to environmental chemicals, they were more likely to have healthy babies, and their babies were better able to cope with environment stressors later in life.

All complex diseases have been shown to have both a genetic and environmental component. A growing body of research is beginning to suggest that many chronic adult diseases and disorders, including asthma, diabetes and obesity, may be traced back to exposures that occur during development. Research supported by the National Institute of Environmental Health Sciences (NIEHS) and others are finding that in utero or neonatal exposures to environmental, dietary and behavioral changes may make people more susceptible to diseases later in life.

The Developmental Hypothesis

The reason people think that susceptibility to disease may be established during pre-birth is due to both human and developmental toxicology studies in animals. Researchers like David Barker, for example, put forward the “fetal programming or developmental basis of health and disease” hypothesis, after finding an association between low birth weight and coronary heart disease. Barker found that a malnourished fetus will adapt its metabolism in the womb to survive until birth, but these changes then increase a person’s risk of disease later in life, such as heart disease, diabetes and possibly cancer. This idea that the human fetus is vulnerable to outside influences, and that what women eat and perhaps even breathe during pregnancy can impact children into adulthood and possibly even future generations as well, is a growing area of research. Little is currently known about the mechanisms by which fetal insults lead to altered programming and to disease later in life.

Timing and Duration of Exposure

From NIH-supported research we know that there are critical periods of vulnerability in the developmental process. This is when cell growth is occurring, tissues are forming, and the body is still without an immune system, blood brain barrier, DNA repair system or any detoxification system to rid itself of chemicals or to protect itself, making the timing and duration of environmental exposures critical. The developmental period is also the most sensitive time for the development of the epigenetic system. This system controls gene expression in tissues and these changes can be transmitted across generations. Thus, changes in the epigenetic system provide a mechanism for environmental exposures to have effects long after the exposure.

The level of response to a given dose may change dramatically depending on the stage of development at which a fetus is exposed. All of this new research is indicating that a “four-century-old paradigm, which states that ‘the dose makes the poison,’ needs to be expanded to emphasize that ‘the timing makes the poison’ as well.

Early Prevention is Critical

If the “developmental basis of disease” hypothesis proves true, then there is an even greater need to change our focus from treating diseases after they are detected to prevention. Doctors have long hoped for ways to prevent or reverse health problems before they become chronic diseases. Given that many disorders arise during fetal development from disruptions in the dynamic but still poorly understood interplay of genes, environment and nutrition, prevention may have to occur decades before a symptom even appears.

Asthma attacks have been linked to exercise, respiratory infections, and exposure to environmental factors such as allergens, tobacco smoke, and indoor and outdoor air pollution. Asthma attacks can be reduced by taking medication and avoiding exposure to known triggers.

A number of studies have reported associations between air pollution exposures and asthma. For example, researchers have found an association between increased hospital admissions for asthma and particulate matter, an outdoor air pollutant.

Air pollution, such as ozone and particle pollution, can make asthma symptoms worse and trigger attacks. Adults and children with asthma are more likely to have symptoms when ozone and particle pollution are in the air. Ozone is often found in smog and particle pollution is often found in haze, smoke, and dust.

Ozone is often worst on hot summer days, especially in the afternoons and early evenings. Particle pollution can be bad any time of year, even in winter. It can be especially bad:

• when the weather is calm, and air pollution can build up,
• near busy roads, during rush hour, and around factories that produce air pollution and,
• when smoke is in the air from wood stoves, fireplaces, or burning vegetation.

Important asthma triggers are:

• environmental tobacco smoke, also known as secondhand smoke;
• dust mites;
• outdoor air pollution;
• cockroach allergen;
• pets;
• mold;
• strenuous physical exercise;
• some medicines;
• bad weather, such as thunderstorms, high humidity, or freezing temperatures;
• some foods and food additives; and strong emotional states that can lead to hyperventilation and an asthma attack.

For millions of women whose lives have been affected by breast cancer, the 1994 discovery of the first breast cancer gene by researchers from the National Institute of Environmental Health Sciences (NIEHS) and their collaborators, was a welcome sign of progress in the fight against this disease. While this discovery and others like it are certainly encouraging, statistics tell us that breast cancer is still a major health concern for women everywhere. According to the American Cancer Society, breast cancer is the most common cancer among women in the United States, other than skin cancer.

Gene-Environment Interactions

For years, NIEHS has played a leadership role in funding and conducting studies on the ways in which environmental exposures increase breast cancer risk. This research includes animal studies to understand the role of environmental agents in the initiation and progression of cancer, as well as research on chemical risk factors and genetic susceptibility in human populations.

Although scientists have identified many risk factors that increase a woman’s chance of developing breast cancer, they do not yet know how these risk factors work together to cause normal cells to become cancerous. Most experts agree that breast cancer is caused by a combination of genetic, hormonal, and environmental factors.

The Sister Study

As new research continues to unravel the mysteries surrounding the causes of breast cancer, NIEHS scientists have recruited more than 50,000 women to participate in a landmark study looking at the possible interplay between genetics and the environment in the development of this disease. The Sister Study includes diverse sisters of women diagnosed with breast cancer from across the country. The researchers are comparing the genetic profiles and environmental exposures of sisters who don’t develop breast cancer with those who do become cancer patients, in order to uncover clues that will help us better understand why some women develop cancer and others do not.

Study volunteers provide samples of their blood, urine, toenail clippings, and household dust, which may be analyzed for pesticides, heavy metals, and other environmental chemicals that may be linked to breast cancer development. The researchers will also look for specific gene variations that may predispose a woman to the effects of cancer causing agents. Women enrolled in the study also complete detailed questionnaires about their health history, past environmental exposures, and lifestyle. The participants then complete yearly follow-up questionnaires to account for changes in their health status or environmental exposures. Additionally, with funding support from the Susan G. Komen for the Cure foundation, NIEHS was able to successfully enroll 1,500 families into the Two Sister Study. Sister Study participants, whose sister had breast cancer under age 50, and their available biological parents were invited to participate in this family-based study. The study aims to investigate the genetic and environmental factors that influence young-onset breast cancer.

Breast Cancer and the Environment Research Program

During early childhood and adolescence, the breast tissue is developing and maturing, and recent studies suggest that environmental exposures, such as certain chemicals, diet, and social factors, during these critical stages of development, may affect breast cancer risk later in life. In an effort to uncover the links between early environmental exposures and cancer risk throughout the course of life, NIEHS is partnering with the National Cancer Institute to support the Breast Cancer and the Environment Research Program (BCERP). The BCERP supports trans-disciplinary research on the interaction of chemical, physical, biological, and social environmental factors with genetic factors during specific developmental windows of susceptibility. The program’s network of scientists, clinicians, and community partners are working in close collaboration on two different approaches — one focusing on puberty in young girls and the other examining other critical windows of susceptibility.

The Puberty Studies are investigating and identifying predictors of early-onset puberty, by studying 1,200 young girls, aged 6 to 8 at the time of enrollment. The girls have periodic visits to assess hallmarks of pubertal development and changes in exposures of interest. The underlying rationale for this study is that early sexual maturation is associated with increased risk of breast cancer, and this may represent a critical period in establishing long-term breast cancer risk. Researchers are focusing on environmental exposures, including chemicals in personal and household products that may be hormonally active; lifestyle factors, such as food intake and physical activity; body size and development; and psychosocial factors. Another component of the program, called the Windows of Susceptibility Studies, is exploring other developmental periods throughout the life span, including in utero and menopause. These investigations could be informative, especially in light of novel findings of the effects of diet, hormone replacement therapy, and long-term exposure to agents, such as endocrine disruptors, in adults, as well as children. Using basic science techniques in laboratory animals, cell cultures, and epidemiological and population studies, researchers are looking how the environment interacts with a person’s genes to affect breast cancer risk. There are also studies looking at how multiple generations can be affected through an individual’s exposure, for example, how the mother’s exposure may affect her child’s susceptibility to breast cancer. Throughout the BCERP, researchers are collaborating with breast cancer advocates and others to build and promote partnerships with community members, public health practitioners, policymakers, and other stakeholders. Across the board, the research findings are being developed into public health messages designed to educate young girls and women about the roles of the environment in breast cancer development, and the importance of reducing their exposures.

Chemical Exposures in Human Populations

In some regions of the country where there is an unusually high incidence of breast cancer, environmental factors have been targeted as a possible cause for this increase. During the 1990s, NIEHS and the National Cancer Institute cofunded the Long Island Breast Cancer Study Project, one of the largest and most comprehensive studies ever conducted on the environmental causes of breast cancer, to investigate the high rate of breast cancer in Long Island, New York. In the study, scientists focused their investigation on three widespread pollutants to which many of the Long Island residents had been exposed — organochlorine pesticides, including DDT and its metabolite DDE; polychlorinated biphenyls, toxic compounds used in electrical transformers; and polycyclic aromatic hydrocarbons (PAHs), a primary component of urban air pollution. Although there was some evidence of a modest increase in the risk of breast cancer from PAH exposure, the researchers did not identify any environmental factors that could be responsible for the high incidence of breast cancer in the Long Island area.4 In a separate study conducted on Long Island women, researchers at Stony Brook University found no association between exposure to electromagnetic fields from residential power use and breast cancer risk.5

Cancer-causing Substances

Scientists are particularly interested in whether exposure to naturally occurring and synthetic chemicals may influence breast cancer risk. This includes exposure to chemicals in the air we breathe, the food and beverages we consume, and the chemicals that come in contact with our skin. The National Toxicology Program, an interagency program headquartered at NIEHS that evaluates agents of public health concern, has listed six substances in its Report on Carcinogens (RoC) that cause or may cause breast cancer in humans.6 These include diethylstilbestrol, a synthetic form of estrogen that was used to prevent miscarriages; steroidal estrogens used for menopausal therapy; X-ray and gamma radiation; alcoholic beverages; tobacco smoking; and the sterilizing agent, ethylene oxide. The RoC also lists over 60 substances that have been shown to cause mammary gland cancer in laboratory animals, including food additives or contaminants, such as byproducts from cooking meats at high temperatures; pharmaceuticals; consumer or manufacturing products, such as flame retardants, chemical solvents, and dyes; industrial chemicals used to make rubber; vinyl and polyurethane foams; pesticides; and environmental pollutants formed largely from burning fuels. Most of these substances also caused tumors at many other tissue sites besides the mammary gland. Few studies in humans have evaluated whether these substances are risk factors for breast cancer, and designing these studies in humans can be challenging. Additionally, NIEHS in-house researchers are finding that early life exposures to some chemicals can alter rodent mammary gland development, disrupt lactation, and may increase susceptibility to breast cancer. The timing of exposures appears to be a critical element in development of adverse outcomes. Knowing that mammary gland development and tumor types are similar between rodents and humans, the researchers are working to develop and encourage the use of mammary gland assessments in developmental research studies, chemical test guidelines, and risk assessments.7 More research is needed to pinpoint the environmental and genetic factors that determine breast cancer susceptibility. Once scientists can identify the elements that are associated with cancer risk, appropriate interventions and precautions can be designed for those who are most likely to develop the disease.

Bladder Cancer

The bladder is the organ in the body that stores urine before it leaves the body. Smoking is the greatest risk factorassociated with bladder cancer. The relationship between bladder cancer and drinking water contamination has also been researched extensively. High levels of arsenic in drinking water have been well-established as causing cancer.

Cancer of the Brain and Central Nervous System

Brain cancer is the growth of abnormal cells in the tissues of the brain and central nervous system including the spinal cord, meninges, and cranial nerves. Little is known about the causes of cancers of the brain and other parts of the central nervous system. Several studies of environmental risk factors have presented inconsistent and inconclusive results.

Childhood Cancers

Researchers have studied childhood cancers for many years but still do not know a lot about what causes them. Finding the causes of childhood cancers is challenging because cancer in children is rare and each type of cancer may have different factors that lead to its development. It is especially difficult to identify environmental factors related to childhood cancer because environmental exposures to the parent, the child in the womb, or the child after birth may play a role.

Childhood acute lymphocytic leukemia

Acute lymphocytic leukemia (ALL, also called acute lymphoblastic leukemia) accounts for about 3 out of 4cases of childhood leukemia. ALL is most common in early childhood, peaking between 2 and 4 years ofage. This leukemia starts from the lymphoid cells in the bone marrow and then spreads to the blood. Fromthere it can go to the lymph nodes, spleen, liver, central nervous system, and other organs.

Childhood acute myeloid leukemia

Acute myelogenous leukemia (AML, also called acute myeloid leukemia) accounts for most of the cases thatare not ALL. Cases of AML are more spread out across the childhood years, although it is slightly morecommon during the first 2 years of life and during the teenage years. This leukemia starts from the cellsthat form white blood cells (other than lymphocytes), red blood cells, or platelets.

Esophageal Cancer

Esophageal cancer is a cancer that forms in the esophagus, a muscular tube in the chest that is part of the digestivetract. Research is needed to better understand the relationship between the environment and esophageal cancer.

Female Breast Cancer

Breast cancer is a tumor that starts from cells of the breast and can spread to distant areas of the body. Otherthan skin cancer, breast cancer is the most commonly diagnosed cancer in women in the United States., but mencan have breast cancer too. The exact causes of breast cancer are unknown; however, there are some known risk factors.

Kidney Cancer

Kidney cancer is a cancer that forms in tissues of the kidneys. Kidney cancer is among the 10 most common cancersin both men and women. Research is needed to better understand the connection between the environment and kidney cancer.

Laryngeal Cancer

Laryngeal cancer is a cancer that forms in the tissues of the larynx. The larynx is also known as the voice box. Research is needed to better understand the relationship between the environment and laryngeal cancer.

Leukemia

Leukemia is cancer of the blood cells. When someone has leukemia, the body makes large numbers of abnormal blood cells. Leukemias are a diverse group of diseases including those listed below. The relationship between leukemia and the environment is still not well understood; however, studies have determined that exposure to high levels of ionizing radiation has been linked to specific types of leukemia in both adults and children.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a type of cancer that starts in the white blood cells (lymphocytes) in the bone marrow. It then invades the blood. Leukemia cells tend to build up in the body over time. In many cases people have no symptoms for at least a few years. Compared to other types of leukemia, CLL usually grows slowly.

Acute myeloid leukemia

Acute myeloid leukemia (AML) goes by many names, including acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia, and acute non-lymphocytic leukemia. "Acute" means that the leukemia canprogress quickly, and if not treated, would probably be fatal in a few months.

AML is a cancer that starts in the cells that are supposed to mature into different types of blood cells. AML starts in the bone marrow (the soft inner part of the bones, where new blood cells are made), butin most cases it quickly moves into the blood. Both children and adults can get leukemia.

Liver Cancer

Liver cancer is a disease in which cancer forms in the liver cells. The liver plays an important role in removingharmful substances from our blood. This includes environmental contaminants people come into contact with duringtheir lifetimes. Even though the liver usually does a good job at removing those harmful substances, certain chemicals have been shown to damage the liver. For example, studies have shown that some people who drink watercontaining high levels of arsenic over many years could experience health effects including liver cancer.

Lung Cancer

Lung cancer forms in the tissue of the lung, usually in the cells lining the air passages. The lungs are the organswe use to breathe. Cigarette smoking is the single most crucial risk factor for, and leading cause of, lung cancer. Exposure to radon is the second leading cause of lung cancer.

Melanoma

Melanoma is a type of cancer in skin cells that produce the pigment that colors the skin (melanin). It is the most dangerous and one of the most common cancers among adolescents and adults under 40. Most melanomas are causedby exposure to ultraviolet (UV) radiation from the sun. However, a growing number of people are being overexposed to sun rays and other sources of artificial UV radiation used in industry and other settings such as indoor tanning (using a tanning bed, booth, or sunlamp).

Mesothelioma

Mesothelioma is a rare form of cancer which is almost always caused by exposure to asbestos. This type of cancer happens when harmful, or malignant, cells develop in the protective lining that covers most of the body's internal organs. The most common sites for mesothelioma are in the chest or belly, where cells become abnormal in response to asbestos fibers that have embedded in the outer lining of the lungs or chest cavity, the lining of the abdominal cavity (belly), or the sac that surrounds the heart.

Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma (also called non-Hodgkin's lymphoma, NHL, or just lymphoma) is a group of cancers that startin lymphoid tissue (also called lymph or lymphatic tissue) and can then spread to other organs. The causes of Non-Hodgkin lymphomas are mostly unknown. Specific viruses, immune deficiency, and specific autoimmune conditions have been implicated in increased risk. However, some environmental issues, including exposures to pesticides and solvents, are also being investigated.

Oral and Pharyngeal Cancer

Oral and pharyngeal cancers, which are cancers of the mouth and throat, include cancers in the tongue, gum, floorof mouth, palate, lip, oral cavity, pharynx, and other areas of the mouth. Research is needed to better understandthe relationship between the environment and oral and pharyngeal cancers.

Pancreatic Cancer

Pancreatic cancer is a cancer that forms in the pancreas, the thin, pear-shaped gland behind the stomach. The pancreas plays an important role in the digestive system by producing fluids to help break down food and hormones to control blood sugar levels. Research is needed to better understand the relationship between the environment and pancreatic cancer.

Testicular Cancer

Testicular cancer affects the testes in men, and it often begins in the cells that make sperm. Testicular cancer is rare and is often curable. Men between the ages of 20-34 years old are the most frequently diagnosed with testicular cancer. The incidence of testicular cancer has risen in the past 20 years, and studies are being conducted to explore possible connections with environmental exposures.

Thyroid Cancer

Thyroid cancer is a cancer that starts in the thyroid gland. The thyroid gland is under the Adam's apple in the frontpart of the neck. The excessive risk for thyroid cancer associated with exposure to external ionizing radiation has been well-established. No other environmental chemicals or physical agents have been associated with this cancer.

Carbon monoxide, or CO, is a toxic gas that you cannot see or smell. It is found in exhaust from cars and trucks, lawn and construction equipment, airplanes, boats, and trains.

CO usually comes from sources in or near your home that are not properly maintained or vented. These sources includeheating systems, water heaters, portable generators, and gas cooking ranges and appliances. CO from these sourcescan build up in a place that does not have a good flow of fresh air.

Indoor and outdoor air pollution exposure has been associated with COPD. The most prominent indoor exposures are from tobacco smoke and the use of biomass fuels, while the most common non-occupational outdoor exposures are particulate matter (PM10 & PM2.5), ozone, pesticides, and sulfur dioxide from automobiles and industrial sources. Occupational exposures such as fumes, gas, and both inorganic and organic dusts have been associated with COPD.

People with COPD are more vulnerable to the effects of air pollution, and at lower levels than people without COPD. Exposure to air pollution has been linked to increases in COPD-related emergency department visits and hospitalizations

People are exposed to a wide range of chemicals during their lives. Chemicals are present in food, clothes, furniture, housing materials, and more. Evidence suggests that many chemicals cause damage to the central nervous system which can impact developmental disabilities. However, much of this evidence is based on studies of groups accidentally exposed or workers exposed to levels above those found in the environment.

Avoiding or reducing children's exposure to harmful chemicals may help prevent some developmental disabilities. Mostscientific studies about how the environment may impact developmental disabilities have been focused on intellectual disabilities and autism spectrum disorders (ASDs).

Intellectual Disabilities

Exposures to lead, polychlorinated biphenyls (PCBs), and methylmercury are well-documented risk factors for intellectual disabilities.

Autism Spectrum Disorders

We do not know all of the causes of ASDs. However, we have learned that there are likely many causes for multipletypes of ASDs. There may be many different factors that make a child more likely to have an ASD, including environmental,biologic and genetic factors.

There is still a lot to learn about environmental contributors to autism and research into some environmental factors is underway.

Climate change and rising temperatures can affect your body in many ways

Extreme heat and unpredictable weather patterns are big news around the world. But did you know that climate change is not just a concern for scientists? It’s also worrying doctors.

Warmer global temperatures cause many environmental changes. These include droughts, increased risk of wildfires, more extreme temperatures, warmer oceans, and stronger storms. These changes can contribute to water-borne illnesses, infectious diseases spread by animals—especially insects such as ticks and mosquitoes—and food contamination. Wildfires release carbon dioxide from trees, and the smoke causes air pollution. Extreme heat can also damage your body.

These climate threats add up over time, which can change human health long-term. Our bodies may struggle more with multiple conditions, and it can also take a toll on our mental health.

Outside temperature affects body temperature

Humans evolved to adjust to their surrounding temperature to stay alive. Sweating is how the body naturally cools itself. But sometimes sweating isn’t enough on especially hot or humid days. The temperature of the Earth is rising, and when they remain high, it’s harder for your body to regulate itself. Hyperthermia is when your body stays too hot and can’t cool itself down. Hyperthermia can take the form of different heat-related illnesses, including:

• Heat cramps. These are muscle cramps, usually in the legs or stomach, caused by loss of salt from sweating. If you start having heat cramps, it’s important to drink lots of fluids, especially those with electrolytes. Also find a cooler space.
• Heat exhaustion. Symptoms include heavy sweating, cold and clammy skin, nausea, and vomiting.
• Heat stroke. This is when your body temperature exceeds 104 degrees Fahrenheit (40 degrees Celsius). Heat stroke can be life-threatening.

Who is most at risk for heat-related illness?

Groups most at risk because they are less able to regulate their body temperature include:

• Infants and children
• Pregnant people
• Older adults
• People who are overweight
• People taking certain medications

People with disabilities or mobility issues may not be able to get to a cooler place if needed. People who work or exercise outside are vulnerable to high heat.

Extreme heat can make chronic diseases worse, including cardiovascular (heart), respiratory (lungs), and cerebrovascular (brain and blood vessels) illnesses. It could also affect diabetes-related conditions, asthma, and chronic obstructive pulmonary disease (COPD).

People with lower incomes may not be able to afford home air conditioning or be able to weatherproof their homes to control temperatures. Those living in major cities are also affected by the urban heat island effect. Human-made surfaces like roads or building walls absorb and re-emit the sun’s heat. This causes surrounding air temperatures to rise.

And some factors—chronic disease, lower incomes, and urban heat islands—are even higher for people of color than for non-Hispanic White people. These groups are more likely to live in environmentally hazardous places due to housing and racial discrimination. Scientists predict that the health risks will be greatest for Black adults and people ages 65 and older.

What can you do to stay safe?

Stay as cool as possible! Remember to:

• Drink plenty of hydrating fluids. Water and sports drinks that replace salts and minerals are best for staying hydrated. Avoid caffeine, alcohol, and beverages with lots of sugar.
• Schedule exercise or outdoor activities when temperatures are lower. Aim for the early morning and evening.
• Get into an air-conditioned space. This can be at home, in the homes of friends and family, or in public places. Community centers, shopping malls, movie theaters, and libraries are some options. Local officials may also designate public spaces as cooling centers during emergencies.
• Dress for heat. Wear breathable clothes with lighter colors and moisture-wicking fabric.

If you have heat edema (swelling in your ankles and feet because you’re feeling hot or sunburned), try elevating your legs. If that doesn’t work quickly, check with a health professional.

Investigators both in the United States and abroad have shown relationships between short- and long- term exposure to particulate air pollution and the increased risk of acute myocardial infarction, referred to as heart attack, and other forms of ischemic heart disease (also known as coronary artery disease or coronary heart disease).

A number of studies have reported associations between air pollution and hospital stays for heart attacks and other forms of heart disease. For example, researchers have demonstrated increases in heart attack hospital stay rates in relation to the levels of fine particles in the air (PM2.5). This relationship is observed particularly in sensitive groups such as the elderly, patients with pre-existing heart disease, survivors of a heart attack, or people with chronic obstructive pulmonary disease.

The level of environmental risk for heart attacks depends on several factors:

• the amount of pollution in the air,
• a person's exposure to the air pollution, and
• overall health.

A heart attack can happen to anyone. Learning which risk factors apply to you can help you take steps to eliminate or reduce your risks.

Lead occurs naturally in the Earth's crust. It is released in the environment during some activities such as mining, manufacturing, and burning fossil fuels.

The main source of childhood lead poisoning is from lead-based paint and lead-contaminated dust in older homes. Lead was once used in paints, gasoline, and vinyl products. It is still used to make batteries, ammunition, some metal pipes, and devices to shield x-rays.

24 million homes have peeling or chipping lead-based paint and high levels of lead-contaminated dust. More than 4 million of these homes have young children living in them.

Health Effects

People may be exposed to lead by breathing or swallowing lead or lead dust. Once it enters the body, lead can become a health hazard. Lead can affect almost every organ and system in the body, especially the nervous system. It can cause learning disabilities and behavioral problems. At very high levels, it can cause seizures, coma, and even death. Lead poisoning frequently goes unrecognized because it often occurs with no obvious symptoms.

Children are more vulnerable to lead poisoning than adults. The first 6 years of life are critical and is the time when the brain grows the fastest. Connections in the brain and nervous system control thought, learning, hearing, movement, behavior, and emotions which are formed during the first 3 years. The normal behavior of children at this age are crawling, exploring, teething, and putting objects in their mouth that puts them into contact with any lead that is present in their environment. .

No safe level of lead exposure has been identified.

Prevention

The key to preventing lead poisoning in children is to stop them from coming into contact with lead; those children who have been poisoned by lead must also be tracked and treated.

Noise pollution

Every day you are surrounded by sounds from your environment, including the TV, radio, appliances, and traffic. Noise pollution is unwanted or bothersome sound. In some cases, noise pollution can be loud enough to damage the ear and contribute to hearing loss. Noise pollution can also disrupt sleep and contribute to chronic stress. These issues have been associated with health conditions like high blood pressure, heart disease, and diabetes.

Sound is measured in units called decibels (dB). Sounds at or below 70 dB are usually safe and won’t harm your hearing. However, sounds can be harmful if they are too loud for even a short time. Occasional loud noises are okay, but it’s important to give your ears time to recover in quiet.

Average sound levels (in dB)

• A typical conversation: 65–80
• Washing machine or dishwasher: 45–65
• Gas-powered lawn mowers and leaf blowers: 80–100
• Motorcycle: 80–110
• Sirens: 110–129
• Fireworks: 140–160

More than 30 million Americans are regularly exposed to hazardous levels of sound.

Ways to protect your hearing

To reduce your risk of hearing damage from noise:

• Move away from the noise
• Wear hearing protectors (such as earplugs or earmuffs)
• Lower the volume (including when wearing headphones)

Light pollution

Artificial light from electronic devices, homes, streetlights, vehicles, and buildings creates light pollution. This can cause problems for people and animals.

Exposure to artificial light at night affects your body’s melatonin production. Melatonin is a hormone that signals it’s time to go to sleep. Poor sleep can affect your focus, judgment, memory, and other bodily processes.

Bright electric lights can also affect birds that migrate at night. These birds can become confused and may fly into buildings, communication towers, and other structures. The U.S. Fish and Wildlife Service estimates that nearly 7 million birds die each year from colliding with communication towers at night.

Ways to reduce artificial light at night

• Keep your room dark for at least 9-10 hours a night.
• Install room-darkening shades on your windows.
• Turn off the lights and electronic devices in the bedroom when you are sleeping. Avoid watching television, using your phone, or working on the computer right before you shut your eyes.
• If you get up in middle of the night to use the bathroom, for example, use a dim red nightlight instead of the regular room light. Red light suppresses melatonin production less than other wavelengths.
• Do not take melatonin tablets unless directed by your health care provider. Melatonin can disrupt your circadian rhythm further.

Our understanding of risk factors for reproductive problems such as infertility, low birth weight, prematurity, fetal and infant death has increased over the past decades. Certain health conditions, social and economic factors, and behaviors can increase the risk of adverse reproductive and birth outcomes. We have also learned that environmental exposures can play a role in reproductive and birth outcomes. However, thereis still much we do not know.

Exposure and Risk

The following are some of the possible environmental exposure and risk factors that are associated with reproductiveand birth outcomes:

• Exposure of nonsmoking pregnant women to environmental tobacco smoke (also known as second hand smoke) may be a risk factor for preterm birth, low birth weight, and possibly fetal death or miscarriage.
• Exposure to air pollution may be related to both low birth weight and preterm birth, even at low levels.
• A pregnant woman's exposure to lead may cause preterm birth, low birth weight, and spontaneous fetal death or miscarriage.
• Exposure to pesticides has been associated with fetal death (miscarriage) and babies being born too small, but more research is needed in this area.
• Although age and certain health conditions are more commonly associated with infertility, it is believed that environmental contaminants may cause infertility by creating other health conditions. For example, some research suggests that environmental contaminants can affect a woman's menstruation and ovulation. Low-level exposures to compounds such as lead and pesticides are suspected risk factors for women. Exposure to compounds such as lead and polychlorinated biphenyls (PCBs) have been linked to decreased sperm quality among men. Much more research needs to be done to find out how environmental contaminants may be affecting human fertility.
• Some scientists have suggested that environmental hazards can affect how many males are born. Parents and the fetus can be exposed to different hazards referred to as endocrine disruptors. Fewer males are conceived when exposure to endocrine disruptors causes a decrease in testosterone. Diethylstilbestrol (DES), a synthetic estrogen widely prescribed to pregnant women during the mid-1900s, is a strong endocrine disruptor. Previous studies have suggested an association between endocrine-disrupting compounds and the secondary sex ratio (the sex ratio of the grandchildren of the exposed women). Several studies show that declines in the sex ratio of males to females at birth may be associated with occupational exposure, or exposure to air pollution.

Prevention

Women who are pregnant or may become pregnant should follow their doctor's advice on how they can have a healthy baby. Doctors can also answer questions on fertility and give advice on conceiving. Early and regular prenatal care helps identify conditions and behaviors that can result in adverse reproductive and birth outcomes.

Here are some ways to prevent environmental exposures:

• Stop smoking and avoid secondhand smoke.
• Limit outdoor activity when the Air Quality Index shows unhealthy levels of air pollutants.
• Cut out or reduce any indoor sources of particulate matter, like wood-burning stoves and fireplaces, and try to reduce the amount of time spent outdoors near areas with higher levels of air pollution, such as areas with a lot of traffic.
• Stay away from lead.
• Stay away from mercury. Some fish, especially albacore tuna, may have been contaminated with mercury. State health departments sendout public fish consumption guidelines that pregnant women can follow.
• Do not use pesticides if you are pregnant. Stay away from rooms that have been recently sprayed with insecticides and from other areas with potential pesticide exposure.

What surrounds you each day in your home, work, or neighborhood and the resources available to you can affect your health. You can’t always choose what’s in the environments you live, work, or play in. But taking small steps to make your environments safer and limiting your exposure to potentially harmful substances can help keep you healthier.

1. Make your home healthier

Take a look around your home. Do you know what’s in your household goods and products? Some chemicals can harm your health if too much gets into your body. Becoming aware of potentially harmful substances and clearing them out can help keep you and your family healthy.

2. Reduce your allergies

A change in season can brighten your days with vibrant new colors. But blooming flowers and falling leaves can usher in more than beautiful backdrops. Airborne substances that irritate your nose can blow in with the weather. When sneezing, itchy eyes, or a runny nose suddenly appears, allergies may be to blame. Take steps to reduce your exposure to allergens.

3. Stay safe during hot weather

Heat is the biggest danger in the summer months. Being hot for too long can cause many illnesses, some of which can be deadly. But the warmer weather also brings lots of new opportunities to improve your health. Here’s how to make the most of the summer months.

4. Guard against cold weather

The frosty air of winter can be invigorating. But cold air can also pose threats to your health, whether you’re indoors or outside. Learn to recognize the signs of your body temperature dropping too low, and take steps to keep yourself and your family warm and safe during the chilly season.

5. Stay safe in the water

Summer is a great time to go out and have fun in the water. But recreational waters—including swimming pools, lakes, and oceans—can sometimes get contaminated with bacteria and viruses. Swimming in contaminated water can make you and your family sick. But you can take steps to stay safer while playing in the water.

6. Air quality and your health

The combination of high temperatures, few winds and breezes, pollution, and airborne particles can brew up an unhealthful mixture in the air, just waiting to enter your lungs. These substances can make it hard to breathe and can sap your energy. If the air quality is especially poor, it may take a few days for your body to recover. And if you’re regularly exposed to high levels of unhealthy air, the health consequences can linger for months or even years.

7. Test for toxic gases

Radon gas typically moves up through the ground and comes into homes through cracks in floors, walls, and foundations. Sometimes it enters the home through well water. Whatever the source, your home can trap radon inside, where it can build up. You might not be able to see or smell radon, but it can still harm you—slowly, and in ways that you can’t detect.