Week 10 Flashcards
PCB Poisoning in Japan 1968 and Taiwan 1979
Oil disease
Pregnant women who were exposed to PCB-contaminated oil gave birth to babies who were small and had dark brown pigmentation of the skin. Follow-up studies of these children found growth impairment, delayed development, clumsiness, and IQ’s averaging around 70
Routes of exposure
- respiratory
- ingestion
- dermal
- fetal transmission
Measuring brain function
- IQ - cognition
- behaviours
- brain imaging
Vulnerability of the developing brain
- the blood brain barrier isn’t fully formed; it is more permeable to toxic chemicals
- rapidly growing cells are often more vulnerable to toxic chemicals that slowly growing cells
- brain growth occurs over a long duration
- the fetus lacks enzymes to detoxify contaminants
- young children are often more heavily exposed to contaminants than older children and adults
Key brain imaging findings in ADHD
Brain areas with reduced size in ADHD:
- frontal cortex
- prefrontal cortex
- cingulate cortex
- basal ganglia - striatum
- caudate, putamen
- cerebellum
polychlorinated biphenyls (PCBs)
- PCBs were used commercially between 1930-1979 for electrical equiment
- banned in open systems 1977, total ban in 1979 (US)
- oily liquids or solids, colorless to light yellow. Stable with flammability
Limitations of studying the impact of toxic chemicals on brain development
- prospective cohorts with biomarkers of exposure are typically modest in size
- some biomarkers of exposure variable and single spot urine is insufficient
- reliance on non-persistent chemicals as biomarkers of exposure in prospective cohorts
- failure to account for variety of other risk factors or test for modification (e.g., folate status, genes)
Summary
- toxic chemicals are linked with learning and behavioural problems at levels thought to be safe
- subtle effects observed in childhood often progress to more serious disease or disabilities
- early life exposure to toxic chemicals are linked with life-long impacts on brain function and behaviour
how to avoid exposures to toxic chemicals
- eat fresh, organic and unpackaged foods
- avoid canned foods
- avoid using pesticides around the home
- avoid cosmetics, fingernail polish and lotions
- demand health agencies update chemical policies and reduce industrial pollutants
- support bans on smoking and pesticides
EDC
Endocrine disruptors chemicals
any substance or material that alters the functions of the endocrine system and consequently causes adverse health effects in a intact organism, its progeny or its (sub)population
Common EDC
Pesticides: DDT, and more
Industrial Chemicals: Bisphenol A, PCBs, etc.
Natural Plant Compounds: phytosptrogens, etc
DDT Exposure
4-fold risk for breast cancer
Obesogens
chemicals causing obesity (thought to be a potential cause)
Phthalate syndrome
DEPH –> reduced AGD –> epididymis malformation, hypospadias, undescended testicles, nipple retention
Summary of EDC
- EDC disrupt hormonal pathways
- evidence linking EDC with human disease and disorders is troubling
- how much evidence is necessary to action to reduce exposure?
