Poultry
Poultry
Poultry
University of California
Poultry

Egg Study Results

In 2018, the UC Davis California backyard chicken egg study was conducted due to concerns about the potential contamination of eggs by heavy metals in the environment. We used Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to analyze backyard chicken eggs from 344 California residences for the presence of 6 naturally occurring metals. These metals have the potential to affect human health when consumed in excessive amounts.

Study Findings:

The table below shows the levels of 6 metals found in eggs submitted to our study. The average, minimum, and maximum micrograms (ug) of these metals per average large egg (57 grams) is listed below. The table shows results from the 602 samples that were submitted:

 

Average (ug/egg)

Minimum (ug/egg)

Maximum (ug/egg)

Level of Concern (daily intake)

Arsenic (As)

0.02

< Detection Limit* 

2.11

10 ug1 

Cadmium (Cd)

0.07

 < Detection Limit*

 2.18

4.1 ug2

70 ug3

Copper (Cu)

36.04

3.88

 179.77

 700 ug4

Lead (Pb)

1.39

 0.04

27.97

 3 ug5

12.5 ug6

Mercury (Hg)

 0.48

< Detection Limit*

 7.13

 11.2 ug7

Nickel (Ni)

0.70

< Detection Limit*

 28.46

770 ug8 

*The detection limit is the minimum concentration at which one can be 99% confident that the measured concentration is distinguishable from a sample that does not contain a detectable amount of the metal of interest.

  1. The California Office of Environmental Health Hazard Assessment (OEHHA) daily threshold for arsenic consumption associated with cancer risks.
  2. The California OEHHA daily threshold of cadmium associated with reproductive harm.
  3. Oral Reference Dose Level for cadmium consumption in food is 0.45 micrograms per pound of body weight per day. The value given is the level of concern for an average 154lb (70kg) adult.
  4. The Agency for Toxic Substances and Disease Registry’s safe consumption threshold of copper is 4.54 micrograms per pound of body weight per day. The value given is the level of concern for an average 154lb (70kg) adult.
  5. The Food and Drug Administration (FDA)'s maximum daily intake (called the Interim Reference Level) of lead for children. Please note that this threshold level is set nearly ten-times less than the actual amount of intake of lead from food required to reach the Center for Disease Control's blood reference level for lead.
  6. The FDA's maximum daily intake of lead for adults. Please note that this threshold level is set nearly ten-times less than the actual amount of intake of lead from food required to reach the Center for Disease Control's blood reference level for lead.
  7. California’s Prop 65 threshold for mercury consumption associated with cancer risks is 0.07 micrograms per pound of body weight per day. The value given is the level of concern for an average 154lb (70kg) adult.
  8. The California OEHHA daily threshold for nickel consumption associated with cancer risk is 5 micrograms per pound of body weight per day. The value given is the level of concern for an average 154lb (70kg) adult.
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