An article published in Science Daily reports on a Taiwanese study that found higher levels of toxic chemicals called dioxins in three chicken eggs from free-range hens compared to three other eggs from free-range hens and 12 eggs from caged hens. Based on their findings, the researchers concluded that free-range eggs may be less healthy to eat.
The study's design – low sample sizes (one egg per location) and unbalanced distribution of collected samples – severely weakens the reliability of the data, yet the reporter does not bring these concerns to the reader's attention. A sample size of one egg per location is not statistically valid, meaning that a researcher cannot determine if what he or she measured was simply a random event.
The article reveals that six free-range eggs and 12 eggs from caged hens were analyzed for dioxins. The 18 eggs were sampled from 18 different locations across Taiwan. Most of the caged eggs came from a different part of Taiwan from the free-range eggs.
The concentrations of dioxins measured in three of the six free-range eggs were similar to concentrations measured in the caged eggs. The elevated dioxin concentrations reported in the study only apply to three of the six free-range eggs.
The researchers' conclusion that free-range eggs may be less safe, based on dioxin measurements from three eggs, is similar to claiming that all M&M's in a bag are brown because you happened to pull out three brown M&M's. To properly assess dioxins in eggs – or colors of M&M's in a bag – a larger number of samples is needed.
That said, given their extreme toxicity, elevated dioxins in any food item warrant further investigation. It is highly likely that soils in Taiwan are heavily contaminated with dioxins in areas where free-range chickens are raised. Like a canary in a coal-mine, the few contaminated eggs found in this study suggest the possibility that many food items grown in or on contaminated Taiwanese soils contain high dioxin levels. Critical reporting should raise this possibility for the reader.
Finally, the author of the news article uses the term "regular" to describe eggs from caged hens, implying that free-range eggs are irregular in some way. In reality, for most of human history, eggs have come from free-range hens. Industrial production of eggs from caged hens is a relatively recent approach that places hens in crowded, often unhealthy conditions and relies heavily on drugs and chemicals – such as antibiotics – to keep the birds disease-free.
The reporter could help the reader put the scientific findings in context by providing perspective on the scientific approach and interpretation of data. Such perspective could be obtained, for example, by interviewing additional scientists who were not related to the study.
