Adolescence is a stressful time. From friends to school to families, stressful situations become common. The body can respond with faster breathing, a pounding heart, tense muscles and beads of sweat. And teens who breathe polluted air appear to respond most strongly to stress, a new study shows. Those with anxiety or depression appear especially sensitive to these pollutant effects.
Air pollution harms health in many ways. People who regularly breathe dirty air are more likely to have immune disorders, heart disease or lung cancer. And the smaller the pollutant particles, the bigger the problem.
Particles less than 2.5 micrometers (0.0001 inch) across seem to wreak the most havoc. These tiny pollutants come from car engines, coal-burning power plants and fireplaces. It would take about 30 of these micro-pollutants to span a human hair. Because they’re so small, they’re easy to breathe in. They irritate the lungs and make people cough. But they don’t stop there. They cross into the bloodstream and reach the brain. And wherever they end up, they can trigger inflammation and other types of harm.
Some studies suggest that air pollution is also linked to mental health problems. However, it hasn’t been clear whether air pollution causes those issues.
Jonas Miller wanted to know whether or how air pollution might affect the body’s response to stress. A psychologist, Miller works at Stanford University in Palo Alto, Calif. He was especially interested in stress in teens. Miller knew adolescence can be full of social challenges. And most tweens and teens spend more time outdoors than do adults, so they can breathe in more of those tiny pollutants.
Miller's team recruited 144 tweens and teens for their study. Most of the kids lived in or near San Francisco, Calif. It ranks among the 10 U.S. cities having the worst air quality. San Francisco also collects data on air pollution throughout the city. Miller used those data to see how polluted the air was near each recruit’s home.
Miller’s team collected physical and social information about the students. They also recorded each recruit’s height and weight and whether they had started puberty. The students also reported where they lived and how much money their parents made. The participants then answered questions about how they felt. For instance, they might answer whether they were anxious or felt liked by others. Each student also visited the lab at Stanford to participate in a stressful test.
Before the test, a researcher hooked each participant up to a heart rate monitor. They put sensors on one hand to measure how much a student sweated. The sensors recorded heart rate and sweat levels for five minutes as the participant rested. Then the test began.
A member of the research team read aloud the beginning of a story. The researcher then told each recruit that they had five minutes to make up an exciting ending to the story. They would have to memorize their ending and present it aloud to a judge.
After finishing this task, the judge had the participant do math problems. If he or she made a mistake, the judge had the student start over. The whole time, sensors recorded heart rate and sweat levels.
At rest, all the students had similar heart rates and sweat levels, Miller found. That was true no matter where they lived or how dirty the air was near their home. But as the test got tough, differences began to emerge. Kids from neighborhoods with more air pollution reacted more strongly to stress. Their heartbeats became irregular. They sweated more than teens who lived in cleaner places. And these effects were twice as strong for students who reported anxiety or depression.
Threats from the air
Anxiety causes fight-or-flight responses. Miller looked at other possible causes of those strong reactions in the students. He considered body mass and stage of puberty. He looked at family income and neighborhood. And he noted whether the participant belonged to a minority racial or ethnic group.
Only air pollution explained the stronger stress response in anxious or depressed teens.
The teens’ “bodies were preparing to deal with possible threats or challenges in the environment,” Miller concludes. Such bodily responses to stress are linked to negative feelings, he notes. Over time, he says, these responses can “contribute to problems with both physical and mental health.”
His team published its findings September 1 in Psychosomatic Medicine.
“This is an interesting study,” says Anjum Hajat, who was not involved with the project. She works at the University of Washington in Seattle. As an epidemiologist, she studies the causes of disease. Miller’s study “provides unique evidence of the negative health impacts of air pollution among adolescents,” she says.
Hajat points out that the study used data on fine (very small) particulates collected at the neighborhood level. “Many existing air-pollution models can accurately predict [such air pollution] at an individual's residence,” she notes. Future studies may provide a more accurate picture of how much air pollution a given person really breathes.
How can teens limit their exposure to air pollution? They “should consider limiting their time outside during rush hour,” Miller says. That’s especially important “on days when air pollution is particularly strong.” Indoors, he notes, using air purifiers with HEPA filters can help reduce exposure to tiny pollutants.
Teens also should get mental help when they need it, Miller says. “Treating symptoms of anxiety and depression can boost people’s resistance to the harmful effects of fine-particle air pollution,” he suspects.
adolescence A transitional stage of physical and psychological development that begins at the onset of puberty, typically between the ages of 11 and 13, and ends with adulthood.
anxious (n. anxiety) A feeling of dread over some potential or upcoming situation, usually one over which someone feels he has little control.
cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
data Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.
depression A low spot, such as in a field or the surface of a rock. (in medicine) A mental illness characterized by persistent sadness and apathy. Although these feelings can be triggered by events, such as the death of a loved one or the move to a new city, that isn’t typically considered an “illness” — unless the symptoms are prolonged and harm an individual’s ability to perform normal daily tasks (such as working, sleeping or interacting with others). People suffering from depression often feel they lack the energy needed to get anything done. They may have difficulty concentrating on things or showing an interest in normal events. Many times, these feelings seem to be triggered by nothing; they can appear out of nowhere.
disorder (in medicine) A condition where the body does not work appropriately, leading to what might be viewed as an illness. This term can sometimes be used interchangeably with disease.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
epidemiologist Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.
fight-or-flight response The body’s response to a threat, either real or imagined. During the fight-or-flight response, digestion shuts down as the body prepares to deal with the threat (fight) or to run away from it (flight).
filter (in chemistry and environmental science) A device or system that allows some materials to pass through but not others, based on their size or some other feature.
heart rate Heart beat; the number of times per minute that the heart — a pump — contracts, moving blood throughout the body.
immune (adj.) Having to do with the immunity. (v.) Able to ward off a particular infection. Alternatively, this term can be used to mean an organism shows no impacts from exposure to a particular poison or process. More generally, the term may signal that something cannot be hurt by a particular drug, disease or chemical.
inflammation (adj. inflammatory) The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It also is an underlying feature responsible for the development and aggravation of many diseases, especially heart disease and diabetes.
information (as opposed to data) Facts provided or trends learned about something or someone, often as a result of studying data.
matter Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."
mental health A term for someone’s emotional, psychological and social well-being. It refers to how people behave on their own and how they interact with others. It includes how people make choices, handle stress and manage fear or anxiety. Poor mental health can be triggered by disease or merely reflect a short-term response to life’s challenges. It can occur in people of any age, from babies to the elderly.
micrometer (sometimes called a micron) One thousandth of a millimeter, or one millionth of a meter. It’s also equivalent to a few one-hundred-thousandths of an inch.
model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.
monitor To test, sample or watch something, especially on a regular or ongoing basis.
particle A minute amount of something.
particulate A tiny bit of something. A term used by pollution scientists to refer to extremely tiny solid particles and liquid droplets in air that can be inhaled into the lungs. So-called coarse particulates are those with a diameter that is 10 micrometers or smaller. Fine particulates have a diameter no bigger than 2.5 micrometers (or 2,500 nanometers). Ultra-fine particulates tend to have a diameter of 0.1 micrometer (100 nanometers) or less. The smaller the particulate, the more easily it can be inhaled deeply into the lungs. Ultra-fine particulates may be small enough to pass through cell walls and into the blood, where they can then move throughout the body.
physical (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.
power plant An industrial facility for generating electricity.
psychologist A scientist or mental-health professional who studies the human mind, especially in relation to actions and behaviors.
puberty A developmental period in humans and other primates when the body undergoes hormonal changes that will result in the maturation of reproductive organs.
recruit (noun) New member of a group or human trial. (verb) To enroll a new member into a research trial. Some may receive money or other compensation for their participation, particularly if they enter the trial healthy.
resistance (as in drug resistance) The reduction in the effectiveness of a drug to cure a disease, usually a microbial infection. (as in disease resistance) The ability of an organism to fight off disease. (as in exercise) A type of rather sedentary exercise that relies on the contraction of muscles to build strength in localized tissues. (in physics) Something that keeps a physical material (such as a block of wood, flow of water or air) from moving freely, usually because it provides friction to impede its motion.
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly. (in biology) The structure that an organism uses to sense attributes of its environment, such as heat, winds, chemicals, moisture, trauma or an attack by predators.
social (adj.) Relating to gatherings of people; a term for animals (or people) that prefer to exist in groups. (noun) A gathering of people, for instance those who belong to a club or other organization, for the purpose of enjoying each other’s company.
stress (in biology) A factor — such as unusual temperatures, movements, moisture or pollution — that affects the health of a species or ecosystem. (in psychology) A mental, physical, emotional or behavioral reaction to an event or circumstance (stressor) that disturbs a person or animal’s usual state of being or places increased demands on a person or animal; psychological stress can be either positive or negative. (in physics) Pressure or tension exerted on a material object.
symptom A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.
tween A child just approaching his or her teenage years. Tween is a term usually used for 11- to 12-years olds.
unique Something that is unlike anything else; the only one of its kind.
Journal: J.G. Miller et al. Fine particle air pollution and physiological reactivity to social stress in adolescence: The moderating role of anxiety and depression. Psychosomatic Medicine. Vol. 81, September 1, 2019, p. 641. doi: 10.1097/PSY.0000000000000714.