I almost drove off the road listening to an ad from a law firm urging parents with children with autism spectrum disorder (ASD) to be part of a lawsuit suing baby food manufacturers for causing their child’s condition. According to the ad, the question of what causes ASD has been settled and what remains is for parents to get what is owed them from baby food manufacturers that have been hiding the truth from the public for years.
Law firms are now actively working to gather clients for class action lawsuits against baby food manufacturers. As is often the case, what you hear or see in the media is far scarier than what you read in scientific journals. I will focus on two metals – arsenic and lead because these are the metals that have the most data on exposure to baby foods.
These lawsuits rely primarily on two studies that found varying levels of arsenic, lead, or cadmium in baby foods: a 2019 Consumer Reports article and a February 2021 Staff Report to the U.S. House of Representatives from the Subcommittee on Economic and Consumer Policy.
Why are these metals found in baby foods?
Arsenic is found in all foods, not just baby foods.
Arsenic is a naturally occurring metal in the earth’s crust, found in soil and water, taken up by plants and fish, and ultimately becomes part of our food chain. The foods that contain the highest levels of arsenic are rice, fish and shellfish, and some meats, although it is also found in grains, fruits, vegetables, cereals, and poultry - just about every food. Arsenic levels tend to be high in rice due to the flooded conditions under which rice is grown, which allows arsenic to be easily absorbed by the rice. Arsenic is present in seawater and enters the food chain through algae. Most seafood contains a harmless organic form of arsenic, Arsenobetaine, not the more toxic inorganic form.
Lead is less commonly found in foods.
Although lead is also a naturally occurring metal in the earth’s crust, a large percentage of environmental lead comes from human activities, such as mining, smelting, combustion of coal and oil, and from past sources (currently regulated) such as lead in gasoline, paint, and solder cans. Food is not a significant source of lead, and the levels found in foods have generally been low. However, the risks from lead exposure from other sources, such as drinking water, soil, and paint chips, should not be dismissed as lead is a known neurotoxin and can damage children’s developing brains at very low levels.
What about the FDA?
FDA does not have standards for metals in baby foods, except for an action level for arsenic in infant rice cereal at 100 ppb. This level is not legally enforceable but is a guidance level for the industry.
Recently, the FDA also set a draft action level of 100 ppb for apple juice and 20 ppb for lead in all other juice types. This is not specific to products marketed for infants or any other age group.
What is the evidence that these metals cause ASD?
Let us look at a review article that examined the available studies on this topic:
A 2019 review examined 14 studies that investigated the association between arsenic and 37 studies that examined the association between lead and ASD. The studies:
- Divided children into two groups – those diagnosed with and those without an ASD diagnosis
- Determined whether there was a statistically significant difference in the measured arsenic or lead levels in the hair, blood, or urine of the two groups of children.
The studies did not determine causality; they identified a correlation.
- Out of the 14 studies on arsenic exposure, 8 (53.3%) reported a positive association.
- Out of the 37 studies on lead exposure, 19 (51.3%) reported a positive association.
With these results showing that slightly more than half of the studies reported a positive association, why did the authors conclude
“There is consistent evidence supporting a positive association between early life arsenic exposure and ASD and inconsistent evidence for lead exposure and ASD risk.”?
Their conclusion was based on meta-analysis, combining the studies and using various statistical methods to come up with a single summary statistic.
Meta-analysis can be tricky. As a non-statistician, I struggle with the concept of combining various studies, each with different experimental designs, and coming up with one answer. It turns out that I am not the only one struggling. In an interesting and entertaining article, I learned that “a meta-analysis is a safer starting point than a single study – but it won’t necessarily be more reliable.”
Among the many reasons:
- There are subjective judgments every step of the way, giving teams of like-minded people plenty of room to steer in a desired direction if they want to
- It is not at all unusual for a meta-analysis to be heavily dominated by a single study
- A meta-analysis is a snapshot in time that can be out-of-date the day it is published, with new research coming almost daily.
The authors of the 2019 review study included eight studies in the meta-analysis, finding statistically more arsenic in the hair or blood of those diagnosed with ASD compared to the controls. However, the authors did not include any studies that measured arsenic in urine in their meta-analysis. In a discussion of the results from all the arsenic studies, the authors state, "The inconsistent findings of the results in these studies make it difficult to conclude the relationship between arsenic exposure and ASD in children.” How, then, did they conclude that there was a consistent association between arsenic and autism?
For lead, 17 studies were included in the meta-analysis, finding statistically more arsenic in the blood of those diagnosed with ASD compared to the controls. There was a statistically significant difference in the studies that measured lead in hair between the ASD group and the control group, but the higher levels were in the control group. Finally, there was no difference in urinary lead between the groups, leading the authors to conclude that the evidence of ASD correlating with lead levels was inconsistent.
What causes ASD?
The answer is that scientists do not know. Although scientists do not know what causes ASD, many believe it is likely a combination of factors, such as the interaction of genes (particularly genetic mutations) and the prenatal environment.
Conclusions
Class action lawsuits are not new in the U.S., but their scientific basis has weakened over the years. The current lawsuits over ASD and baby foods are based on weak scientific evidence of an association, where even the researchers cannot show a consistent association and no evidence that baby foods cause ASD.
