Introduction

Exposure to environmental toxicants can occur through

• air,
• contaminated soil,
• food,
• intravenous exposure, such as to phthalates leaching from blood bags and intravenous tubing,
• transplacental exposure of a fetus, and
• water.

This section will examine the following sources of contamination:

• diet,
• in-home indoor air contaminants,
• "take-home" contaminants from parents' work sites,
• other settings: child care, school, and work settings (work settings for adolescents),
• neighborhood,
• cultural practices and folk medicine, and
• disaster-related exposures.

Diet-Breast milk

Breast feeding is encouraged as the optimal form of nutrition for most infants by the American Academy of Pediatrics (AAP) [AAP 1997] and the World Health Organization (WHO) [WHO 1994]. In spite of these recommendations, however, patients may still voice concerns about the passage of chemicals from breast milk into their infants.

Because human milk contains high levels of fat (i.e., about 4%), lipophilic chemical compounds are preferentially taken up in breast milk [Schreiber 2001], resulting in exposure to the nursing infant. For some industrial chemicals such as dichlorodiphenylchloroethane (DDE) and certain solvents, breast milk concentrations are threefold to tenfold greater than corresponding maternal blood levels [AAP 2001]. Still, nonlipophilic chemicals such as the heavy metals (e.g., lead, mercury, cadmium, arsenic) do not bind to fat and do not accumulate to higher levels in breast milk than they do in blood [Solomon and Weiss 2002].

Very few instances of harm have occurred in a nursing baby due to ingesting chemicals found in breast milk. The instances of harm that have occurred have been due to episodes of gross poisoning of the mother such as

• the Yusho and Yucheng episodes of dioxin/furan contamination of rice oil in Japan and China [Pronczuk et al. 2002] and
• deaths of breastfeeding infants in Turkey whose mothers had accidentally eaten some seed used in bread-making that was contaminated with hexachlororbenzene [Solomon and Weiss 2002].

The many benefits to the infant provided by breastfeeding, such as immune factors and growth factors that aid brain development, greatly outweigh any risks from environmentally low levels of contaminants in breast milk [Landrigan et al. 2002]. In fact, for most contaminants in utero exposure is a greater contamination source than is breast milk [Pronczuk et al. 2002]. A good resource to consult when discussing possible breast milk contaminants is AAP's Pediatric Environmental Health, a handbook for pediatricians found at http://ebooks.aap.org/product/pediatric-environmental-health [AAP 2003a].

Diet-Older Infants and Toddlers

As children mature, the composition of their diet changes. Newborns' and young infants' diets consist of breast milk and formula. New foods such as fruits, vegetables, and fruit juices are added to older infants' and toddlers' diets. For example, infants and toddlers often consume many apple products and apple juice. But toddlers' food preferences are often limited. They might prefer only a few foods for relatively long periods of time. This might result in a greater exposure per kilogram of body weight to any toxicants found in those foods.

Diet-Special populations

Children whose families subsist heavily on marine mammals and fish may suffer from excess exposures to any toxicants these animals might carry. Toxicants in marine subsistence foods might include persistent organic pollutants and mercury.

In-home Contamination of Indoor Air

In-home contamination sources are numerous. Listed below are examples.

• Carbon monoxide from faulty furnaces or heaters.
• Insulation material.
• Lead, primarily from peeling paint.
• Mold.
• Nitrogen dioxide, primarily from combustion of gas-powered appliances (e.g., gas ranges).
• Pesticides.
• Secondhand tobacco smoke.
• Solvents.
• Radon.

Take-home Contamination

"Take-home" contamination refers to the transmission of potentially toxic quantities of industrial agents from occupational settings to homes and residences. Also referred to as paraoccupational exposure, take-home contamination has been more vividly referred to as "fouling one's own nest." Unlike the environmental contamination that affects many people over large geographic areas (e.g., air pollution, spills of industrial chemicals, accumulation of toxic wastes), take-home contamination affects the immediate families of involved workers.

Industrial toxicants can be carried from the workplace to the home on

• clothing,
• hair,
• shoes,
• skin, and
• tools.

Small children are often most susceptible to the dangers associated with "take-home" contamination. Numerous reports document lead contamination among the children of lead workers [Whelan et al. 1997]. In such cases, preschool children sometimes had blood lead levels equal to or greater than those found in parents working with or around lead. The highest blood levels of mercury documented in young children were seen following take-home contamination by mercury-exposed workers involved in thermometer manufacturing [Schreiber 2001].

Take-home contamination can occur even when appropriate precautions appear in place. For example, requiring contaminated workers to change clothing and shoes before returning home is not enough. Because some exposure risks are associated with laundering contaminated work clothes, no one should bring such clothing home to be cleaned. Instead, these clothes should be professionally laundered, preferably as part of the employer's occupational safety program. Showering at work may also be necessary in some settings to ensure that contaminants are removed from hair and skin. But this may not always be possible when work occurs at construction sites or other outdoor areas.

Other Settings

Time spent in child care settings, schools, and occupational settings for adolescents may result in significant opportunities for hazardous substance overexposure. For example, a recent survey showed that the pesticide-exposure related incidence of illnesses in children in schools is 7.4 cases per million U.S. schoolchildren (1998-2002) [Alarcon et al. 2005].

Neighborhoods

Potentially toxic exposure sources for children might appear in many places in the community. See the Table below for point sources of exposure as well as possible hazards.

Table 1. Neighborhood sources of exposure and possible contaminants

Cultural Practices and Folk Medicine

Cultural practices such as the use of azogue (i.e., use of elemental mercury in magico-religious ceremonies) may contaminate a dwelling and expose children. And some folk medicines have been contaminated with heavy metals such as lead [Woolf and Woolf 2005; CDC 1993, 2002].

Disaster-Related Exposures

Chemical disasters

Children are particularly threatened by chemical disasters. The 1984 accidental discharge from a pesticide plant in Bhopal, India, exposed over 100,000 persons to a cloud of methyl isocyanate. A sizable number of children died and a disproportionate number of children suffered comas, seizures, and ophthalmologic and pulmonary toxic effects from their exposure [Irani and Mahashur 1986; Mehta et al. 1990].

Terrorist attacks

The attack on the World Trade Center (WTC) created an enormous environmental disaster. WTC dust was found to consist predominantly (95%) of coarse particles and contained

• asbestos,
• glass fibers,
• lead,
• polychlorinated biphenyls (PCBs),
• polychlorinated furans and dioxins,
• polycyclic aromatic hydrocarbons (PAHs), and
• pulverized cement [Landrigan et al. 2004a].

Studies are underway to document and evaluate health effects in contaminant-related exposures, including rescuers, clean-up workers, and other exposed persons, including children. Asthma diagnoses increased in children exposed to the WTC disaster [Thomas P et al. 2008]. Follow-up of 182 pregnant women who were either inside or near the WTC on September 11^th, showed a 2-fold increase in small for gestational-age infants [Landrigan et al. 2004b].

Progress Check