Lead continued Nov 29, 2005

1
Lead continued Nov 29, 2005 Lead Storage and
HalfLife Blood - 35 days Brain about 2
years Bone decades Blood lead reflects recent
exposure and mobilization from bone. Bone
demineralization is increased when Calcium
deficient.
2

• The Special Case of Fetal and Early Childhood
  Exposure
• dual contributions to maternal blood lead levels
  Pb stored in bone and newly acquired
• bone demineralization common in pg
• maternal and umbilical cord blood levels are
  about equal
• exposure to fetus
• exposure through breast milk
• direct postnatal exposure via ingestion or
  respiration

3
Childhood Symptoms Severe poisoning usually
seen at gt 70 micrograms/dL some reports at
50 1st signs - lethargy, abdominal cramps,
anorexia and irritability After days to weeks
in infants lt 2 years - vomiting, clumsiness and
ataxia, then alternating periods of
hyperirritability and stupor, finally coma and
seizures. Death or survival with severe
cognitive deficits borderline to mental
retardation
4

• Effects at 12-54 micrograms/dL blood level
• Children at highest risk often live in higly
  disadvantaged circumstances related to poverty
  confounds judgments of effects due to Pb
• Best work by Needleman et al - white,
  English-speaking children from working class to
  upper middle class backgrounds
• reduced IQ
• reduced verbal ability
• reduced attention span
• sensory impairments
• As blood lead goes from 10-20 micrograms/dL, IQ
  declines by 1- 3 points
• When blood lead is around 30, IQ decrements are
  about 5-15 points.

5
Effects in range of 15-25 micrograms/dL -
include all effects at lower levels shown on next
slide - Changes in auditory threshold - reduced
social and emotional functioning problematic or
antisocial behaviors increased
6
Effects at lt 10 micrograms/dL Seen on tests of
specific neuropsychological functions not on IQ
level, but on specific abilities - impaired
attention and increased perseveration - reduced
visual-spatial construction abilities (block
design puzzles) - reduced fine motor
coordination abilities and motor speed and
dexterity - reduced sociability - changes in
brainstem auditory evoked responses These effects
persist into adulthood judged to be permanent.
7
US Regulatory History Year Upper end of
acceptable range (micrograms/dL) 1960 60 1970
40 1975 30 1985 25 1991 10 Should it be
lower?
8

• History of Food Safety
• established for disease prevention from
  foodborne pathogens
• 1920s focus added to nutritional content of
  foods
• in mid1900s, focus added/shifted to preventing
  chronic conditions, cardiovascular disease
• morphed into the optimal dietary intake focus
  supplements
• 1970s and 1980s concern about food additives
• 1990s to present awareness of pesticide
  residues, heavy metals and PCBs in fish, etc
• All now responsibility of FDA some shared
  responsibility with EPA and CDC.

9
Major regulatory roles played by FDA The Food
Safety and Inspection Service (FSIS) part of
the US Dept of Agriculture EPA (water quality
air quality impact food/water supply) National
Marine Fisheries Service CDC monitoring of
outbreaks of contamination
10
Collective Concerns for Todays FDA Biological
pathogens (e.g., bacteria, viruses, parasites)
Naturally occurring toxins (e.g., mycotoxins,
paralytic shellfish poison) Dietary
supplements (e.g., ephedra) Pesticide residues
Toxic metals (e.g., lead, mercury)
Decomposition and filth (e.g., insect fragments)
Food allergens (e.g., eggs, peanuts, wheat,
milk) Nutrient concerns (e.g., vitamin D
overdose, pediatric iron toxicity) Dietary
components (e.g., fat, cholesterol)
Radionuclides (radioactive substances in water
or food) Mad Cow and other diseases Product
tampering Genetically engineered foods
11
What is an additive? Nutritional
supplements Cosmetic Additives in foods
coloring, flavoring agents Preservatives Processin
g Aids emulsifiers stabilizers thickeners
agents that improve packaging survival of
quality
12

• The FDA exclusively regulates additives full
  responsibility
• the type of food an additive can be used in
• 2. the maximum quantity that can be used and the
  information that must appear on the label.
  (100-fold margin of safety)
• 3. Manufacturersnot FDAare responsible for
  proving the safety of an additive before it can
  be approved. Safety is not defined by law but
  by FDA to be a reasonable certainty of no harm
  under intended use conditions.
• Intended use applies to food consumption not
  worker exposure.