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Quarterly Consult April 2007: Environmental Health Resource

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The Quarterly Consult is a quarterly supplement to the Bulletin highlighting pediatric clinical expertise. If you have an item of interest to include in the Quarterly Consult, contact Dr. Steve Dassel at 206-625-7373, mailbox 8588.

By Steve Dassel, MD

Seattle Children's Hospital and the University of Washington (UW) share a unique resource in pediatric environmental health. I interviewed Dr. Catherine Karr, acting assistant professor, general pediatrics, and Dr. Sheela Sathyanarayana, pediatric environmental health fellow, general pediatrics. Dr. Karr directs the UW Pediatric Environmental Health Specialty Unit (PEHSU) and has an adjunct appointment in the School of Public Health's Department of Occupational and Environmental Health Sciences.

Q: What is the PEHSU?

A: The PEHSU is a free telephone consultation service on pediatric environmental health for health-care providers, government officials, communities, school officials and families. Our multidisciplinary team includes experts from the fields of pediatric and environmental/occupational medicine, clinical and developmental toxicology, industrial hygiene and exposure assessment. In addition, we can provide outpatient or inpatient clinical consultations for pediatric environmental cases. We work collaboratively with the Washington Poison Center, which forwards questions from our toll-free phone number (1-877-KID-CHEM). We can also be reached at 206-744-9380 or through our website, www.depts.washington.edu/pehsu/. The Poison Center remains the first line for acute poisoning concerns, while we offer special expertise in addressing chronic environmental health impacts and low-dose exposure questions. We also provide outreach and education for health professionals throughout Washington, Alaska, Idaho and Oregon.

Q: What does the PEHSU address?

A: We provide information on the diagnosis, treatment and prevention of pediatric illnesses due to preconception, prenatal, perinatal and childhood exposures to environmental hazards. We answer questions regarding appropriate environmental health laboratory test selection, interpretation of findings or treatment. Exposures may come from contaminated air, water, soil or food; routes include oral, dermal or inhalation. They can be man-made contaminants, such as pesticides, flame retardants and plasticizers, or naturally occurring contaminants, such as radon, mold or arsenic. Using an evidence-based approach, we address environmental health concerns by assessing the relationship between exposure, dose, toxicity and overall health for individuals, or for a community. For example, we conducted a health assessment of lead in drinking water at Seattle schools.

Q: Why is environmental health important for pediatrics?

A: Children are more vulnerable to the consequences of exposure to environmental contaminants. Pound for pound, they take in more water, food and air than adults, so the dose received from a contaminated source is greater than for adults. They are also more susceptible to exposures. For example, children have hand-to-mouth behavior and play close to the ground, increasing their exposure to toxins that settle in dust, soil or carpets. In addition, they have immature metabolic pathways — a disadvantage in detoxifying and excreting toxins. Finally, because their organs undergo tremendous growth and development, toxicant insults early on can have profound downstream effects.

Q: Could you tell me about some common pediatric health problems in your field?

A: The classic concerns continue to be exposure to environmental tobacco smoke, sun exposure and lead poisoning. Increasingly, the new major pediatric morbidities — ADHD, asthma and obesity — are being linked with low-dose exposures to environmental toxicants. For these complex conditions, genetic susceptibility likely works with environmental factors, leading to an increased risk of development or exacerbation of these diseases.

Q: Other than food, how is obesity an environmental health problem?

A: The environment we create for children affects the amount of physical activity they have on a daily basis (e.g., walkability of communities, access to playgrounds, parks and sports fields). There are also emerging data from animal studies that demonstrate an influence of commonly encountered chemicals in consumer products (e.g., bisphenol A and phthalates) on metabolic/endocrine set points. These models show that maternal in utero exposures increase incidence of obesity in offspring. Studies to evaluate these effects in humans are ongoing.

Q: What about respiratory problems related to the environment?

A: Many genetic and environmental factors contribute to the pathogenesis of asthma. Both indoor and outdoor pollutants can trigger exacerbations (cockroach, dust mite and pet allergens; tobacco smoke; mold/damp environments; irritant chemicals in cleaning products; traffic-related air pollutants, such as ozone and particulate matter). Studies are focusing on the link between early-life exposure to environmental factors and induction of incident asthma. The AAP has affirmed the value of the tools for environmental management of pediatric asthma found on http://www.neetf.org/health/asthma/asthmaguidelines.htm.

Q: Is lead poisoning a problem here?

A: Our limited surveillance efforts in Washington state suggest overall prevalence is lower than in many other states. However, children with elevated blood lead levels (BLLs) are identified in our state each year. Without an index of suspicion in clinical practice and screening, we probably miss a lot of at-risk children who may have increased blood lead concentrations. We recommend routine screening using a BLL test for all economically disadvantaged children and Medicaid enrollees at age 12 months and 24 months (or at age 36 to 72 months, if not previously screened). We also recommend routine screening for immigrant children and foreign adoptees, children who reside in central or eastern Washington, and children with neurodevelopmental or neurobehavioral problems, including ADHD.

Lead has been removed from gasoline and most paint products that are now on the market. However, lead-based paint in houses built before 1970 is still a primary source of lead exposure for preschool-aged children, as it chips, peels or is removed during renovation, so screening children in these homes is recommended. Lead may also leach into water from lead- containing pipes, solder and fixtures. We have two other local sources in Washington state — the now retired Asarco smelter, which left a footprint of soil contamination in western Washington, and the historical use of lead arsenical insecticides in central and eastern Washington orchards. There are a variety of other less traditional sources of exposure that likely affect children, such as imported candies, medicinals, jewelry and vinyl lunch boxes.

Low lead exposures have been associated with a variety of neurodevelopmental effects, which include decreased cognition (IQ), inattention and hyperactivity, and juvenile delinquency. No threshold or safe level of exposure to the adverse neurotoxicant effects have been identified — underscoring the importance of reducing exposure.

Q: What is the current recommendation for treatment of lead poisoning?

A: While primary prevention is the main goal (removing sources of exposure), secondary prevention through screening will identify children with elevated blood lead levels and provide opportunity for preventing ongoing excessive exposure. The only approved therapeutic modality is chelation therapy, but it is reserved for BLLs that are quite high (greater than 44 mcg/dL). For lower levels, the effectiveness has not been demonstrated, and identifying and removing ongoing exposure is the focus. For specific guidelines, see http://www.cdc.gov/nceh/lead/CaseManagement/caseManage_main.htm.

Any chelation therapy should be undertaken only under the supervision of a board-certified clinical toxicologist or occupational/environmental medicine specialist with experience in lead toxicity management.

Q: What about vaccine mercury?

A: Like any environmental or drug exposure, the potential for harm is influenced by dose and the form of the toxic agent. The vaccine preservative thimerosal contains ethyl mercury, while the mercury found in some fish is methyl mercury — both are organic forms of mercury. We know less about ethyl mercury, but overall, the toxicity information suggests it is less harmful. Due to theoretical concerns about the potential dose received in early life from multiple vaccines, ethyl mercury has been phased out of all childhood vaccines except some influenza vaccine sources. Many good epidemiological studies have accumulated to refute a link between child exposure to vaccines/thimerosal and the diagnosis of autism.

Q: What about fish mercury?

A: Methyl mercury found in some fish is a potent neurodevelopmental toxicant, especially during fetal and early life exposure. The FDA and the EPA endorse specific prevention guidelines. For all women of childbearing age and young children, the following is recommended: 1) Consistently high methyl mercury concentrations are found in shark, swordfish, king mackerel and tilefish and these should not be eaten. 2) Up to 12 ounces — about two portions a week — of a variety of fish and shellfish that have less mercury may be consumed. Examples are shrimp, canned light tuna, salmon, pollock and catfish. Albacore tuna has more mercury than canned light tuna, and the recommendation is up to six ounces or one average meal of albacore tuna per week.

If your patients eat fish from local waterways, check local advisories. If no advice is available, your patients should eat up to six ounces per week of fish caught from these waters, and refrain from consuming any other fish during that week.

Q: What resources about environmental exposures and outcomes are available?

A: In addition to our PEHSU, the AAP Handbook of Pediatric Environmental Health (also known as the Green Book) is a handy shelf reference that addresses common childhood environmental exposures and appropriate diagnosis and treatment. This book is free for requesting AAP members and trainees. Otherwise you can order it on the AAP website: http://ebooks.aap.org/product/pediatric-environmental-health-3rd-edition.

Q: Do you have any suggestions for PCPs about incorporating environmental health measures into our practices?

A: Start by incorporating an environmental history in your everyday practice and becoming familiar with the basic resources available to you. There are some excellent materials on doing a quick screening on environmental history available from http://www.neefusa.org/health/PEHI/HistoryForm.htm.

Q: What mistakes do you see PCPs making in this field?

A: Not thinking about environmental exposure in the differential diagnosis of a sick child or ordering an inappropriate "environmental" test.

Q: Thank you Sheela and Catherine.

Pediatric Environmental Health Training Program
Learn about environmental threats to children's health, exposure prevention strategies and tools for your practice at "Pediatric Environmental Health Toolkit Training Program: Clinical Applications for the Busy Pediatric and Family Practice." The conference will be held Thursday, May 24, from 8 a.m. to 1 p.m. in the Graham Visitors Center at the University of Washington Arboretum. It is organized by Washington Physicians for Social Responsibility and endorsed by the University of Washington Pediatric Environmental Health Specialty Unit. Contact Nancy Dickeman at nancyd@wpsr.org to register.

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