Children of all ages have unique characteristics that may make them particularly vulnerable to potentially harmful effects of certain environmental contaminants. Children aged 0-5 years are often the population most at risk for these harmful effects because of their unique vulnerabilities (Morgan et al., 2004; Somers, Harvey, & Rusnak, 2011; U.S. Environmental Protection Agency [U.S. EPA], 2006; Wilson et al., 2004). Infants and young children drink, eat, and breathe more as compared to adults on a per-body-weight basis (U.S. EPA, 2008). Unique behavioral differences such as crawling and mouthing activities further increase the potential for children's exposure to harmful environmental contaminants at home and in the community (Faustman, Silbernagel, Fenske, Burbache, & Ponce, 2000). Infants and children are also rapidly growing and developing within a relatively short time frame and windows of vulnerability to adverse health effects associated with early life stage exposure to toxic chemicals are more pronounced (Grandjean & Landrigan, 2006; Morgan et al., 2004; Selevan, Kimmel, & Mendola, 2000).
More than 11 million children aged five years and younger are cared for in early learning environments (ELEs), or settings that provide care for young children (American Academy of Pediatrics [AAP], 2012; National Association for Child Care Resources and Referral Agency [NACCRRA], 2010). Children of working parents and guardians spend on average 40 hours a week in child care (AAP, 2012). Over 360,000 licensed ELEs are operating in the U.S., including about 240,000 family child cares (FCCs) or home programs and approximately 120,000 child care centers (CCCs), which are usually housed in nonresidential facilities (NACCRRA, 2012; National Child Care Information and Technical Assistance Center & National Association for Regulatory Administration [NCCIC & NARA], 2010). In some states, FCCs are further categorized into small (up to six children) and large (7-12 children) settings.
No mandatory federal licensing standards exist for ELEs. Oversight of ELEs is generally carried out by state and local governments. Many state and local licensing authorities refer to voluntary guidelines contained in "Caring for Our Children" (CFOC), a publication of the U.S. Department of Health and Human Services (HHS) in collaboration with the American Public Health Association (APHA) and the American Academy of Pediatrics (AAP), to create licensing and regulatory standards. CFOC serves as a guide for establishing basic health and safety requirements for care providers (AAP, APHA, National Resource Center for Health and Safety in Child Care and Early Education, 2011). The latest edition of CFOC has put a greater emphasis on environmental health in child care settings.
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Ensuring the health and safety of children is a key focus of ELE requirements; however, these concerns should be broadened to include greater emphasis on environmental health protection. The purpose of this article is to discuss children's unique vulnerabilities to certain environmental contaminants that may be present in ELEs, including findings from studies of children's exposure and hazard differences and surveys that have collected information about policies and practices currently used to protect children's environmental health in and around licensed facilities. The information gleaned from these resources is important because it helps to highlight risks and suggests opportunities for reducing children's exposure to contaminants.
Materials and Methods
A large number of studies on the topic of environmental exposures and the developing infant and child are available (U.S. EPA, 2011). This information has been compiled and reviewed by the U.S. Environmental Protection Agency (U.S. EPA) to create handbooks for use in performing human health risk assessments and related analyses (U.S. EPA, 2008, 2011).
Very few major research projects have studied environmental exposures in ELEs. Findings were obtained primarily from three federally funded studies:
* The 2008 Child Care Licensing Survey (NCCIC & NARA, 2010), which provides a snapshot of the licensing standards in all 50 states and Washington, DC. The National Child Care Information and Technical Assistance Center and the National Association for Regulatory Administration (NARA) have recently completed the collection of surveys for the 2011 Child Care Licensing Survey; results are not publicly available at this time but will be posted on the NARA Web site (NARA, 2013);
* The First National Environmental Health Survey of Child Care Centers, or the CCC survey (Tulve et al., 2006; U.S. Department of Housing and Urban Development [HUD], 2003). The CCC survey includes an analysis of lead distribution, lead paint presence, and lead content in dust and soil samples in 168 nationally represented child care centers in the 48 contiguous U.S. states; and
* The Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) looked for the presence of pesticide residues including residues of neurotoxic organophosphate and organochlorine pesticides and other chemicals including phthalates, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in ELEs (Morgan et al., 2004; Wilson et al., 2004). Exposure data for the CTEPP study were collected from 257 preschool children and caregivers in facilities in North Carolina and Ohio. This article will present information as a narrative overview using proven methods of analysis (Green, Johnson, & Adams, 2006).
Results and Discussion
Children's Exposures to Environmental Contaminants
Food and Water Consumption Children have a less diverse diet compared to adults. Therefore infants and young children may consume greater proportions of certain foods and beverages as well as any chemicals that may be present. For example, children between birth and five months of age consume about 19 g/kg/day of apples, compared to adults who consume approximately 2 g/ kg/day, which is almost a 10-fold difference (Firestone, Moya, Cohen-Hubal, Zartarian, & Xue, 2007).
The diet of infants consists primarily of liquids (U.S. EPA, 2011), with a greater proportion of milk compared to teens and adults (Figure 1). Infants less than one month of age have, on average, a daily drinking water intake more than 10 times greater than adults ages 18 to 21 years (Figure 2; Kahn & Stralka, 2009; U.S. EPA, 2011). If the drinking water supply contains environmental contaminants, an infant's exposure to these contaminants could be about 10 times greater than that of a young adult simply because of this relatively larger intake of water. Infants fed reconstituted formula might also be exposed to high amounts of minerals either in the formula, the drinking water, or both, leading to high levels of ingestion of otherwise beneficial minerals. For example, potentially dangerous levels of fluoride and manganese present in both drinking water and some formulas may be ingested (Brown & Foos, 2010; Levy et al., 1995; U.S. EPA, 2008). Excessive exposure to fluoride in the diet may cause tooth pitting, and exposure to high levels of manganese may affect neurological development (Brown & Foos, 2010; Claus Henn et al., 2010; World Health Organization, 2012).
Infants and young children spend a great deal of time in active play on the ground and on floors where contaminants can accumulate in soil, dust, and carpet fibers. Soil and household dust have been found to contain environmental contaminants such as pesticide residues, PAHs, phthalates, lead, pests, and pest droppings that when ingested may cause harm to infants and young children (Table 1; Morgan et al., 2004; U.S. EPA, 2010). Unique behaviors, such as mouthing hands and objects, increase children's exposure to these and other contaminants (Faustman et al., 2000). As a result, children in ELEs may be at risk of exposure to any number of contaminants at any given time.
Structural differences in the upper respiratory tract may cause young children to experience greater penetration of contaminants to their lower respiratory tract as compared to adults (U.S. EPA, 2008). Frequent physical activity of growing children can also lead to increased inhalation rates, which may result in greater exposure risks to environmental contaminants. Even at rest, children have higher breathing rates and increased risks for inhalation of potentially harmful compounds (U.S. EPA, 2011). Children spend 80%-90% more time indoors than adults, and may be at greater risk for exposure to indoor air contaminants (AAP, 2012).
Differences in Children's Physiology Children are physiologically different from adults and undergo rapid periods of growth and development from birth to five years of age (Centers for Disease Control and Prevention [CDC], 2011a; Firestone et al., 2007). During the first year of life, the average newborn's motor skills progress drastically from smiling and controlling head movements to crawling and walking unassisted (Johnson, Moore, & Jeffries, 1978). By the age of three, a child has all of her/his primary teeth and is able to speak clearly using words in the correct context.
Life stages, or "time frames characterized by unique and relatively stable behavioral and/or physiological characteristics associated with development and growth" occur from birth and into adulthood (Firestone et al., 2007; U.S. EPA, 2006, 2011). Children experience more distinctly different phases of growth and development before the age of five as compared to later years of development. Life stages from birth to age five include periods of immunological development, neurological development, bone growth and ossification including dental, liver enzyme activity, and respiratory development.
Infants and young children may experience serious and sometimes lifelong consequences that adversely impact the...