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Children’s environmental healthNovember 9 2004

Don WigleInstitute of Population HealthUniversity of [email protected]

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Outline

Environmental links to selected child health outcomes

• incident asthma, asthma episodes• neuropsychologic deficits among

school-age children at “low-level” lead exposure

• cancer– childhood cancer– adult cancers linked to childhood

exposures.

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Level of epidemiologic evidence for causal relationships

Sufficient evidence - based on peer-reviewed reports of expert groups or authoritative reviews

Limited evidence - several epidemiologic studies, including at least one case-control or cohort study, showed fairly consistent associations and evidence of exposure-risk relationships after control for potential confounders

Inadequate evidence - epidemiologic studies limited in number and quality, inconsistent results, little or no evidence of exposure-risk relationships

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Incident asthma

Sufficient evidence - house dust mite antigens

Limited evidence - ETS, cockroach antigen, outdoor air pollution (e.g., outdoor activities in high-ozone areas)

Inadequate evidence - pet allergens, endotoxins, fungi, pollen, VOCs, formaldehyde, pesticides

Main source: Institute of Medicine. Clearing the air. National Academy Press 2000

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Asthma episodes

Sufficient evidence - ETS, cat, cockroach and house dust mite antigens, outdoor air pollution (e.g., personal NO2, ozone, PM10)

Limited evidence - dog antigens, indoor & outdoor molds, formaldehyde

Inadequate evidence - endotoxins, pollens, pesticides, VOCs, NO2, plasticizers

Main source: Institute of Medicine. Clearing the air. National Academy Press 2000

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Neuropsychologic deficits in school-age children: low-level postnatal

lead exposure

Sufficient evidence - cognitive deficits, visual-motor integration deficits, attention deficits (? sufficient)

Limited evidence - fine motor function deficits, increased hearing threshold, central auditory processing deficits, problem behaviours (incl hyperactivity), academic achievement deficits

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Childhood cancerSufficient evidence• a given radiation dose appears to double the excess

lifetime risk of fatal cancer for children compared to adults

• leukemia - prenatal x-ray pelvimetry (rel. high-dose)• thyroid cancer - incidence < 5 yr after Chernobyl

incident

Limited evidence• leukemia - parental and/or childhood pesticide

exposure, paternal smoking, childhood ionizing radiation (x-rays), nuclear testing fallout, EMF, paternal occupational exposure to solvents, paints and motor vehicle repair/related activities

• lymphomas - parental and/or childhood pesticide exposure, paternal smoking, parental occupational exposure to solvents and other petroleum products

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Childhood cancer (limited evid, cont’d)

• brain - parental and/or childhood pesticide exposure, paternal smoking, paternal occupational exposure to paints

• Wilm’s tumour, Ewing’s sarcoma - parental occupational pesticide exposure

• neuroblastoma - parental occupational lead or pesticide exposure

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Childhood cancer: inadequate evidence

• leukemia - lead, arsenic, indoor/outdoor air pollution (e.g. benzene), radon, RF radiation, chlorination disinfection by-products, paternal radiation exposure (ionizing, EMF)

• brain - radon, EMF, RF radiation, drinking water nitrate/nitrite, paternal exposure to EMF

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Adult cancer: childhood exposures

Sufficient evidence• breast - atomic bomb survivors, fluoroscopy• brain, thyroid - radiotherapy of benign conditions• leukemia - atomic bomb survivors• melanoma - intense sun exposure

Limited evidence• thyroid - nuclear test radioactive fallout• lung - environmental tobacco smoke• stomach - H. pylori (waterborne infection)

Inadequate evidence• testicular - hormonally-active contaminants

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To be ignorant of what happened before one was born is to remain ever a child

Cicero, 55 BC

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Alice Hamilton (1869-1970)

- trained in medicine, pathology, bacteriology

- pioneer in industrial toxicology

- 1919 - first female professor at Harvard

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May 20, 1925 meeting on TEL convened by US Treasury Dept

• Andrew Mellon, Treasury Secretary

– in charge of US Public Health Service

– major owner of Gulf Oil, holder of exclusive contract to distribute leaded gasoline in the southeastern USA

• Alice Hamilton stated that

– lead is a cumulative poison lacking obvious symptoms

– lead poisoning is a serious public health issue

December 1925: expert committee approved use of TEL

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Lincoln, Nebraska, 1933

- test marketing of ethanol blends was common in the US Midwest

- failed due to the market dominance of oil companies

http://www.radford.edu/~wkovarik/papers/fuel.html

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MMT (methylcyclopentadienyl manganese tricarbonyl)

– 1997: Canada bans MMT; Ethyl Corp sues Canada under NAFTA

– 1998: Canada apologizes to Ethyl, pays $13 million, reverses ban and states that MMT is not an environmental or health risk

MTBE (methyl tert-butyl ether)

– 1999: Calif announces MTBE phaseout starting in 2003; Vancouver-based Methanex Corp sues Calif for $970M under NAFTA

– 2002 - MTBE ban delayed until 2004

– 2003 - US Congress act states that no gasoline additive can be considered a "defective product”, virtually blocking lawsuits

Gasoline additives: the sequel

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Evidence to action: role of scientists

• Identify important CEH knowledge gaps and seek research funding

• Support scientific organizations that advocate increased CEH research funding

• Educate the public on important research findings, knowledge gaps and their policy implications

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Evidence to action: scientific barriers

Lack of consensus re epidemiologic evidence

• inadequate studies• unexplained inconsistencies between

well-conducted studies • unknown biologic mechanism• different perspectives of

multidisciplinary expert groups

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Child health and the environment

Chapters

1. Child health and the environment

2. Environmental epidemiology

3. Risk assessment

4. Metals- lead

5. Metals- mercury, arsenic, cadmium, and manganese

6. PCBs, dioxins, and related compounds

7. Pesticides8. Hormonally active agents9. Radiation10. Indoor air11. Outdor air12. Water13. Conclusion

Oxford University Press 2003ISBN: 0-19-51355-98 http://www.mclaughlincentre.ca

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Chapter structure

• Health effects - molecular mechanisms, prenatal outcomes, reproductive toxicity, neurotoxicity, cancer, other

• Exposure - internal dose (biomarkers), environmental contaminant levels, trends

• Risk management - major sources (air, water, food, dust/soil), standards/guidelines, uncertainties

• Conclusion - proven health outcomes, knowledge gaps, risk management issues

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Reference, location

Design Exposure Results Associationa DRa Covariates

(Infante-Rivard et al. 1999), Montreal

Case-control study, 491 cases acute lymphoblastic leukemia (ALL), 491 controls, age < 10 yr; conducted PCR-RFLP and multiplex PCR to detect polymorphisms in CYP1A1, CYP2D6, GSTT1 and GSTM1 genes

Self-reported home use of pesticides in and around house during prenatal period (beginning 1 month before conception) and childhood; pesticides used likely included chlorpyrifos, diazinon, dichlorvos, malathion, cygon, propoxur, chlordane and 2,4-D

ALL associated with maternal prenatal use of herbicides in garden/yard or indoors (odds ratio, yes vs no); similar association for use during childhood

1.8 (CI 1.3-2.6)

Matched for age, sex, geographic region; adjusted for maternal age and education

Exposure-risk relationship between ALL and maternal prenatal use of herbicides indoors or in garden/yard (odds ratio, > 5 times vs 0)

3.7 (CI 0.7-19)

+ As above

ALL associated with maternal prenatal indoor use of plant insecticides (odds ratio, yes vs no); similar association for use during childhood

2.0 (CI 1.3-2.9)

As above

Exposure-risk relationship between ALL and maternal prenatal use of plant insecticides indoors or outdoors (odds

4.0 (CI 1.1-14)

+ As above

www.mclaughlincentre.ca