An Introduction to Children's Environmental Health

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An Introduction to

Children's Environmental Health

 

This piece provides a brief overview of why children's

environmental health is a growing cause for concern.

Although by no means a comprehensive review of this

complex subject, this piece includes a discussion of

why children are more vulnerable than adults to

environmental exposures, what types of exposures

affect children, and which children are at particular

risk.

 

Children today live in an environment that is vastly

different from that of previous generations.

Explosions in technology, information, population and

material goods mark the end of the 20th century. One

of the key contributions to the current technological

age has been the discovery and use of thousands of new

chemicals. During the last 50 years hundreds of

thousands of chemicals have been developed and the

production of synthetic chemicals has increased from

1.3 billion lbs. in 1940 to 320 billion lbs. in 1980.1

Chemicals are ubiquitous in our environment worldwide,

and traces of man-made chemical compounds (toxicants)

are found in all humans and animals.2

 

Currently, use of more than 70,000 chemicals is

allowed in the United States. Little is known about

the health effects of the majority of these chemicals

on children.3 In the last several decades, health

effects due to chemical exposures have been noted in

wildlife.4 Exposures to environmental toxins, such as

lead, are now known to cause permanent damage to a

child's nervous system.5 Other toxicants are being

implicated in causing adverse health effects in

children.6,7 While exposures to some environmental

hazards have decreased because of new regulations and

standards, children continue to be exposed to

toxicants in the air, water and food.8

 

The elegance and delicacy of the development of a

human being from conception through adolescence

affords particular windows of vulnerability to

environmental hazards. Exposure at those moments of

vulnerability can lead to permanent and irreversible

damage. In order to protect children more effectively

and proactively, we must consider why children are

more vulnerable than adults, what types of exposures

affect children and which children are at particular

risk.

 

Why are Children Not Just " Little Adults " When It

Comes to Environmental Exposures?

 

As Ken Olden, Director of the National Institute of

Environmental Health Sciences (part of the National

Institutes of Health) has stated, " A little kid goes

from a single cell to a laughing, sociable,

intelligent, friendly human being over a course of two

years that's dramatic growth and development. " 9

 

Children, beginning at the fetal stage and continuing

through adolescence, are physiologically very

different from adults. They are in a dynamic state of

growth, with cells multiplying and organ systems

developing at a rapid rate. At birth their nervous,

respiratory, reproductive and immune systems are not

yet fully developed. In the first four months of life

an infant more than doubles its weight. Young children

breathe more rapidly and take in more air in

proportion to their body weight than do adults. They

also have higher metabolic rates and a higher

proportionate intake of food and liquid than do

adults.10

 

The rate at which children absorb nutrients from the

gastrointestinal tract is likewise different than the

rate for adults, a fact that can impact their exposure

to toxicants. For example, children have a greater

need for calcium for bone development than do adults

and will absorb more of this element when it is

present in the gastrointestinal tract. When lead has

been ingested into the gut, however, the body will

absorb it in place of calcium. Consequently, an adult

will absorb 10% of ingested lead, while a toddler will

absorb 50% of ingested lead.11

 

Because metabolic systems are still developing in the

fetus and child, their ability to detoxify and excrete

toxins differs from that of adults. This difference is

sometimes to the child's advantage, but more

frequently they are not able to excrete toxins as well

as adults, and thus are more vulnerable to them.12

ALIGN= " JUSTIFY " >Not only does a child's physiology

differ from an adult's, so does its environment. In

its first environment, its mother's womb, the fetus

may be permanently damaged by exposure to a wide

variety of chemicals that can cross into its

bloodstream through the placenta. These chemicals

include lead,13 polychlorinated biphenyls,14

methylmercury,15 ethanol and nicotine from

environmental tobacco smoke.11 Researchers are also

looking at possible connections between health

abnormalities and a group of chemicals called

endocrine disruptors, which mimic the body's hormones

and have been shown to disrupt reproductive and

hormone systems in wildlife.

 

Behaviors characteristic of early childhood also

affect a child's exposure to toxicants. In the first

year of life the young child spends hours close to the

ground where he or she may be exposed to toxicants in

dust, soil and carpets as well as to pesticide vapors

in low-lying layers of air.

 

Normal development in early childhood includes a great

deal of hand-to-mouth behavior, providing another

avenue for exposure to such toxicants as lead in paint

dust or chips and to pesticide residues.

 

Children also spend more time outdoors than do most

adults, often engaged in vigorous play. Because

children breathe more air per pound of body weight

than adults and because their respiratory systems are

still developing, they are prone to greater exposure

to and potential adverse effects from air

particulates, ozone and other chemicals that pollute

outdoor air.16,17

 

Finally, a child's diet differs in important ways from

that of an adult. Because children eat more fruits and

vegetables and drink more liquids in proportion to

their body weight, their potential exposure to

ingested toxicants such as lead, pesticides, and

nitrates is greater. For example, the average infant's

daily consumption of six ounces of formula or breast

milk per kilogram of body weight is equivalent to an

adult male drinking 50 eight-ounce glasses of milk a

day.11 Likewise, proportionate to its body weight, the

average one-year-old eats two to seven times more

grapes, bananas, pears, carrots and broccoli than an

adult.18

 

Two other concerns bear addressing. Because they are

exposed to toxicants at an earlier age than adults,

children have more time to develop

environmentally-triggered diseases with long latency

periods, such as cancer and possibly Parkinson's

disease.19 The effects of multiple and/or cumulative

exposures to toxicants and their potential synergistic

effects are also not known and demand further

research.

 

Which Children Are Most Affected?

 

All children are affected by environmental hazards.

Pollution and environmental degradation know no

county, state, regional, or national border.

Contaminants are transported through many media

including air, water, soil and food throughout the

world. However, children living in poverty and

children in racial or ethnic communities are at

disproportionate risk for exposure to environmental

hazards.

 

According to 1994 Census data, 21%, or more than 14

million children in the US live in poverty.20 Poverty

can compound the adverse effects of exposure to

toxicants because it is so often associated with

inadequate housing, poor nutrition, and limited access

to health care. A primary source of exposure to lead,

for example, is from flaking lead-based paint, a

condition that is more common in poorly-maintained

older housing often found in low-income neighborhoods.

 

Higher rates of poverty are one of the factors that

place children of ethnic and minority communities at

disproportionate risk for environmental exposures.

While 16% of white, non-Hispanic children live in

poverty, the rates in the African-American and

Hispanic communities are 415 and 41%, respectively.20

 

Race has also been shown to be a factor in increased

rates of exposure to certain environmental hazards. An

estimated 2.75 million to 3.85 million children (one

out of four) live within one mile of a National

Priorities List hazardous waste site.

African-American, Hispanic-American and

Native-American children are over-represented in these

communities. A 1987 study conducted by the United

Church of Christ showed that the racial composition of

neighborhoods was a major factor in the placement of

hazardous waste facilities in the US .21 A 1993 study

conducted on race and toxic waste sites confirmed

racial disparities in the placement of facilities.22

In California, all three of the Class I toxic waste

dumps are in or near Hispanic communities.23 Sixty

percent of Hispanics versus 315 of non-Hispanic whites

live in counties of the US in which levels of at least

two or more pollutants exceed EPA air quality

standards.24

 

The health status of children belonging to low-income

and racial and ethnic communities reflects their

increased risk of exposure to environmental hazards.

Eight percent of low-income children are lead-poisoned

compared to 1.9% of middle- and 1.0% of high-income

children. African-American and Mexican-American

children have higher rates of lead poisoning than

white non-Hispanic children (11.2% and 4.0%

respectively, compared to 2.15).25 Rates for

asthma-related deaths and hospitalizations are

routinely higher for African-American children than

for Caucasian children. Coupling the risk factors of

poverty with environmental exposures places children

in racial and ethnic communities at multifactorial

risk for illness.

 

Selected Known Hazards for Children

 

Children face myriad environmental hazards radiation,

solvents, asbestos, mercury, arsenic, sulfur dioxide

and ozone, to name but a few. They fall into

categories such as neurotoxins, endocrine disruptors,

carcinogens, and respiratory irritants and

inflammatants. Discussed below are three selected

environmental hazards known to seriously impact

children's health.

 

Lead

 

* Phase 2 of the Third National Health and

Nutrition Examination Survey (conducted from October

1991 to September 1994) indicated that 930,000

preschool children in the US had blood lead levels

above the Centers for Disease Control and Prevention

(CDC) intervention level of 10 mg/dL;25 nearly 275,000

had blood lead levels greater than 15 mg/dL and nearly

85,000 had greater than twice the CDC intervention

level (20 mg/dL).26 Exposure to lead has been

associated with an array of neurodevelopmental

effects, including attention deficits, decreased IQ

scores, hyperactivity and juvenile delinquency.27,28

Research has also shown an association between

slightly elevated blood lead levels in children at the

age of 24 months and lower general cognitive function

at 5 years of age.29

 

The elimination of lead from gasoline in the

1970s, one of the great public health success stories

of that decade, resulted in significant decreases in

blood lead levels.30 Although lead has been removed

from most paint products now on the market, lead-based

paint in older homes is still the most common source

of high-dose lead exposure for preschool-aged

children. Nationwide, approximately 3 million tons of

lead remain in an estimated 57 million occupied

private housing units built before 1980, a figure that

represents 74% of the nation's housing stock.31

Childhood lead exposures can occur through ingestion

of paint chips or dust from deteriorating surfaces,

from chewing on painted cribs, or through inhalation

of lead paint dust produced by sanding during

renovation.30 Lead is also found in drinking water as

a result of leaching from lead-soldered plumbing and

in soil containing lead residues from automobile

exhaust.6

 

Air Pollution

 

* Air pollution affects children more than adults

because of their narrow airways, more rapid rate of

respiration, and the fact that they inhale more

pollutants per pound of body weight.32 Common indoor

air pollutants include carbon monoxide, radon,

environmental tobacco smoke, asbestos, formaldehyde

and mercury. Common outdoor air pollutants include

ozone and particulate matter.

 

Health effects associated with both indoor and

outdoor air pollution include increased perinatal

mortality, increased acute respiratory illnesses

(e.g., bronchitis and pneumonia), aggravation of

asthma, increased frequency of physician visits for

chronic cough and ear infections, and decreases in

lung function.17 Researchers are seeking to identify

indoor and outdoor air pollutants that serve to

exacerbate asthma. Among persons under the age of 20,

the prevalence of asthma increased by 42% between 1980

and 1987. A recent study of neonatal mortality found

an association between elevated concentrations of fine

particulates and neonatal deaths, including sudden

infant death syndrome (SIDS).34 There is little doubt

that high levels of air pollution are responsible for

increased morbidity, and in some cases mortality, in

children.17

 

Ironically, increases in indoor air pollution

can be attributed to what are generally considered to

be improvements in our quality of life. These include

energy saving measures such as better insulation and

decreased ventilation rates in houses, increased

furnishings, increased mean indoor temperature and

increased indoor humidity.35 In addition, the number

of " airtight " buildings has increased since the 1970s,

as has the use of synthetic building materials and

unvented combustion appliances.36 These factors

coupled with an increase in the amount of time we

spend indoors, have increased the concentration of

indoor environmental pollutants and our exposure to

them.

 

In the outdoor environment, there has been an

effort to reduce exposure to ozone and particulates.

Ozone, the most pervasive air pollutant in the United

States, is produced when hydrocarbons and nitrogen

oxides emitted from motor vehicles and other sources

react in the presence of sunlight.37 Exposure to ozone

has been associated with increased asthma rates in

children38 as well as a reduction in lung function,

and also causes exercise-related wheezing, coughing

and chest tightness.37 During 1991-93, ozone levels

exceeded the National Ambient Air Quality Standard on

four or more occasions in 104 cities or counties, an

area that encompasses 24% of the US population under

the age of 13. African-American, Asian/Pacific

Islander and Hispanic children are disproportionately

represented in areas that exceed acceptable ozone

levels.37 Most recently the US Environmental

Protection Agency has issued regulations to decrease

the levels of ozone and air particulates in outdoor

air.

 

Pesticides

 

* Children are often exposed to toxicants through

the agricultural and home use of pesticides or the

ingestion of pesticide residues on food or in water.

Pesticides used today generally fit into five main

categories: insecticides, herbicides, fungicides,

nematocides and rodenticides.39 Increased awareness of

acute pesticide poisoning has led to an apparent

decrease in acute episodes of toxicity, and public

health concern has thus shifted to evaluating the

effects of low level chronic pesticide exposures.39

Again, children may be more vulnerable than adults to

experiencing latent or delayed effects over the long

course of their lifetime. Researchers have become

concerned about the potential associations between

chronic pesticide exposures and chemical

carcinogenesis, environmental estrogen disruption and

developmental neurotoxicity.39 A 1993 National Academy

of Sciences report stated that some pesticides may

interfere with physiological processes of the child,

including the immune, respiratory and neurological

systems.10

 

Childhood Diseases

 

The US has seen a worrisome increase in certain

childhood diseases, and researchers are working hard

to determine whether this increase is linked to

environmental exposures. As noted, childhood asthma

has increased by more than 40% since 1980, affecting

more than 4.2 million children under the age of 18

nationwide. The incidence of two types of childhood

cancers has risen significantly over the past 15

years: acute lymphocytic leukemia is up 10% and brain

tumors are up more than 30%.40 Although there are no

registries for learning disabilities and attention

deficit disorders among children, there has been

growing attention in recent years to an apparent

increase in both.

 

Policy Implications

 

The key to protection is prevention. Recently, there

has been a dramatic shift in the recognition of

children's environmental health issues in Congress and

federal agencies. In November 1996, the US

Environmental Protection Agency (EPA) released a

report, Environmental Health Threats to Children and

announced that for the first time children would be

considered in all EPA risk-assessment and

standard-setting procedures. Congress passed the Food

Quality Protection Act in September 1996, which

specifically focuses on setting standards to protect

children from pesticide residues and other hazards in

foods. This legislation is based on recommendations

from a ground-breaking research report published in

1993 by the National Research Council entitled

Pesticides in the Diets of Infants and Children. In

April 1997, President Clinton signed an Executive

Order on Children's Environmental Health and Safety

(#13045) requiring federal agencies to include

children and their unique susceptibilities in

standard-setting procedures and establishing an

interagency task force to ensure coordination of

regulations and research. These actions provide an

important framework for protecting children. Whether

they prove to be effective will depend on how

diligently they are implemented.

 

Questions Needing Further Exploration

 

Informed and effective policy is reliant upon

knowledge and understanding of the effects of

environmental hazards on children's health. Research

that identifies patterns of environmental diseases in

children, assesses children's exposures to

environmental toxicants, determines developmental

periods of vulnerability, and quantifies dose-response

relationships will bring us closer to preventive

interventions. Larger research issues must be

addressed to improve our understanding of the

relationship between environmental exposures and

health outcomes in children. These include an

understanding of:

 

the developmental process, including the critical

periods of vulnerability during which environmental

exposures can cause adverse health effects

 

the environmental exposures that occur early in life

and their relationship to the development of adult

disease and to transgenerational effects (health

effects that occur in the child or subsequent

offspring of the person who is exposed to an

environmental toxin)

 

the health effects of low level exposures to

environmental toxicants such as dioxins, endocrine

disruptors and lead

 

the health effects of cumulative and multiple

exposures to environmental hazards

 

the behavioral outcomes that result from environmental

damage to the nervous system

 

the effects on the immune and reproductive systems and

the resultant disease outcomes

 

References

 

1 Diagnosing and Treating Environmental Health

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2 Colborn T, Dumanoski D and Myers JP. Our Stolen

Future. New York, NY: Dutton, 1996.

 

3 Schaefer M. Children and Toxic Substances:

Confronting a Major Public Health Challenge.

Environmental Health Perspectives 1994;102(Supp

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4 Colborn T. Chemically Induced Alterations on Sexual

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5 Goldstein GW. Neurologic Concepts of Lead Poisoning

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6 Meadows R. Growing Pains. Environmental Health

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7 Goldman L. Case Studies of Environmental Risks to

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8 Pirkle JL, Brody DJ and Gunter EW. The Decline in

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1994;272:284-291.

 

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11 Bearer CF. " Environmental Health Hazards: How

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13 Rabinowitz MB and Needleman HL. " Temporal Changes

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21 Commission for Racial Justice United Church of

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22 Goldman BA and Fitton L. Toxic Wastes and Race

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Policy Alternatives, 1994.

 

23 Cole SW. Empowerment as the Key to Environmental

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24 Wernette DR and Nieves LA. Breathing Polluted Air:

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25 CDC. " Update: Blood Lead Levels United States,

1991‚1994 " MMWR, February, 1997.

 

26 Pirkle JL, Brody DJ and Gunter EW. " The Decline in

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1994;272:284-291.

 

27 Needleman HL and Gastonis CA. " Low-Level Lead

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28 Needleman HL, Riess JA, Tobin MJ, Biesecker GE and

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29 Bellinger D, et al. " Low-Level Exposure and

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31 U.S. Bureau of the Census. Statistical Abstract,

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33 American Lung Association. Danger Zones: Ozone Air

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36 Samet JM, Marbury MC and Spengler JD. " Health

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37 CDC. " Children at Risk from Ozone Air Pollution

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38 CDC. " Populations at Risk from Air Pollution United

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39 Reigart JR. " Pesticides and Children. " Pediatric

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40 Bleyer AW. " What Can Be Learned About Childhood

Cancer from 'Cancer Statistics Review 1973-1988' " .

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