Evidence Library

This lesson provides the foundational research so you can evaluate claims yourself, stay current with new findings, and understand why the recommendations in this module are made.

Landmark Studies

Lead

Lanphear et al. (2005) - "Low-Level Environmental Lead Exposure and Children's Intellectual Function" Pooled analysis of 1,333 children showing IQ effects at blood lead levels previously considered safe. Established no threshold for harm.

Needleman et al. (1979) - "Deficits in psychologic and classroom performance of children with elevated dentine lead levels" Groundbreaking study linking lead in baby teeth to classroom behavior and IQ deficits.

Mercury

Grandjean et al. (1997) - Faroe Islands cohort Showed cognitive deficits from prenatal methylmercury exposure at levels previously considered safe.

Pesticides

Bouchard et al. (2011) - "Prenatal Exposure to Organophosphate Pesticides and IQ in 7-Year-Old Children" CHAMACOS study showing 5.5-point IQ deficit per 10-fold increase in prenatal organophosphate exposure.

Fluoride

Bashash et al. (2017) - "Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years" NIH-funded ELEMENT study showing 4-point IQ drop per 0.5 mg/L increase in maternal urinary fluoride.

Endocrine Disruptors

Swan et al. (2017) - "Temporal trends in sperm count" Meta-analysis documenting 52% decline in sperm concentration among Western men from 1973-2011.

Key Researchers to Follow

• Philippe Grandjean, MD - Harvard, developmental neurotoxicology
• Bruce Lanphear, MD - Lead exposure research
• Leonardo Trasande, MD - NYU, EDCs and child health
• Shanna Swan, PhD - Mount Sinai, reproductive epidemiology
• Linda Birnbaum, PhD - Former NIEHS director

How to Evaluate Research

Study design hierarchy:

1. Randomized controlled trials (rare for toxins—you can't ethically expose people)
2. Prospective cohort studies (follow exposure over time)
3. Cross-sectional studies (snapshot associations)
4. Case-control studies (compare cases to controls)

What to look for:

• Peer-reviewed journal
• Adequate sample size
• Appropriate controls for confounders
• Dose-response relationship
• Biological plausibility

Red flags:

• Industry funding without disclosure
• Cherry-picked outcomes
• No replication by independent researchers
• Results that contradict large body of evidence

Staying Current

• Environmental Health Perspectives - Open access NIH journal
• PubMed alerts - Set up for key terms
• Environmental Working Group - Translates research for consumers
• Collaborative on Health and the Environment - Research database