Disclosure: Warren Kindzierski is an adjunct professor in the School of Public Health at the University of Alberta
Canadians woke up Tuesday morning to national and international media reports of a drinking water crisis uncovered by supposed intrepid reporters.
Even CBS news is reporting that “hundreds of thousands of Canadians have been unwittingly exposed to high levels of lead in their drinking water, according to a yearlong investigation conducted by more than
120 journalists” and “lead in Canada’s drinking water worse than Flint crisis.”
The “Flint crisis” is a lead-tainted water pipe issue in Flint, Michigan. The City of Flint switched its drinking water supply from Lake Huron to the Flint River in 2014. After the switch, lead began leaching from water pipes into the drinking water. Bales of media hay were made about this crisis.
Back then the CBC exclaimed, “For 18 months, the people of Flint, Mich., were drinking water laced with a toxic stew of chemicals, including lead.”
What is the supposed drinking water crisis Canadians are facing?
Back in 2016 Health Canada reviewed health effects information on lead exposure with the intent of updating the Canadian drinking water guideline for lead.
They stated, “The strongest association observed to date is between increased BLLs [blood lead levels] in children and reductions in intelligence quotient (IQ) scores”.
They also stated, “The threshold below which lead is no longer associated with adverse neurodevelopmental effects cannot be identified.”
In March of this year they lowered the lead drinking water guideline from 10 to 5 micrograms per litre.
Up until 2012, the U.S. Centers for Disease Control and Prevention identified children as having a blood lead “level of concern” if there was 10 or more micrograms of lead per deciliter (one-tenth of a liter) of blood. They now use 5 micrograms of lead per deciliter of blood for their benchmark. The “no-threshold” assumption of Health Canada speculates that adverse neurodevelopmental effects can occur right down to almost 0 micrograms of lead per deciliter of blood. Their claim is that preschoolers can be exposed to drinking water containing minuscule amounts of lead. This, they
speculate, is enough to impair neurodevelopment and result in permanent intellectual deficits later in life.
Neurodevelopment refers to the brain’s development of neurological pathways that influence performance of intellectual ability, reading ability, social skills, etc. Intelligence involves abilities to learn and adapt to changing environs. Intelligence is challenging to study. This is because it can be defined and measured in different ways. Many studies rely on a simplistic measure called the intelligence quotient (IQ) score.
Cognitive psychology researchers have studied intelligence for decades. Drawing upon these studies, the U.S. National Institutes of Health states that… “genetic factors underlie about 50 percent of the difference
in intelligence among individuals”. Intelligence can also be influenced by other factors – socioeconomic status, parental education, parenting skills, availability of learning resources, nutrition and childhood diseases.
Science is the method
To support lowering the drinking water guideline for lead, Health Canada placed heavy emphasis on a 2005 meta-analysis study. This meta-analysis study claimed that a “statistical correlation” exists between IQ score declines and low blood lead levels in young children.
Meta-analysis is a statistical method that combines data from multiple scientific studies. But it is so flexible that it allows you to selectively choose (cherry-pick) which studies and which data from these studies to combine to get the answer you want. It’s perfect for leaping from molehills of data to mountains of questionable causal claims. A modest review of meta-analysis reveals that it can be loaded with biases and uncertainty.
Health Canada, in their review, ignored the issue of what IQ score testing actually represents. Does it reflect a test takers’ genetic characteristic present at birth, their opportunities and challenges, neither, or both? This issue has provoked much scientific dispute over the years.
Human ability cannot be simply measured by a single IQ test score. These scores as traditionally measured are less significant and more flexible than many scientists believe. Nassim Taleb, a statistician whose work focuses on randomness, probability and uncertainty problems, states that “IQ measures an inferior form of intelligence, stripped of 2nd order effects.”
Even prominent lead researchers, Needleman and Bellinger, admit limitations of standardized IQ tests, stating in 1992 that “[a] global measure, such as an intelligence test, may not be the most valid or
sensitive measure of the quality, efficiency, or flexibility of a child’s cognition or of any effects lead may have on it.” This is because cognitive function is a result of complex, context-dependent interplay among
numerous aspects of information processing.
Also ignored in the Health Canada review was historical evidence on blood lead from the U.S. Centers for Disease Control Advisory Committee on Childhood Lead Poisoning Prevention. In 2007, this committee reported that over 88 percent (about 15 million) of 1970s-era preschool children in the U.S. had blood lead levels greater than 10 micrograms per decilitre.
For the “no-threshold” assumption to be real, this enormous-sized child cohort moving into adulthood should have translated into massive, observable public health problems associated with permanent
intellectual deficits beyond the 1980s. However, this is simply not the case as medical literature in the U.S. is absent of any such evidence.
Finally, blood lead has never risen to a level of being singled out as an important environmental influence in cognitive psychology intelligence studies. What has been singled out is that environmental influences
tend to decline over time and these influences appear to be less important in shaping intelligence later in life.
Cognitive psychology researchers have even stated that “shared environmental influences on IQ decline [decrease] from childhood to adulthood so that these influences might not have an impact in the
Meanwhile back in Flint, Michigan, actual blood lead levels in children before and during their supposed lead-tainted water pipe crisis were reported in March 2019. Scientists compiled blood lead level data for Flint preschool children for three time periods. Two 18-month periods before the supposed crisis were compared to an 18-month period during the supposed crisis.
The scientists found that children’s blood lead levels during the supposed crisis period were actually lower than levels compared to the earlier time periods.
They even stated that… “The data does not support the concept of a global BLL [blood lead level] increase to merit the stigma nor the opprobrium [negative press] of a generation of children with permanent intellectual deficits.”
The world of junk science and junk policy
All of this evidence falsifies the Health Canada “no-threshold” assumption. What is unfortunate is that governments today are swarming with policymakers who would never a let a fake crisis go to waste.
Hence the lowered lead drinking water guideline.
More unfortunate is the fact that city water utilities – meaning you the taxpayer – will be left to foot the bill for any increased lead monitoring and other actions dictated by government under the guise of “the science told us to”.
While lead levels in drinking water may exceed overly protective guidelines, there is no real evidence that anyone is being permanently harmed from drinking water with traces of lead.
To base scientific judgments and policy decisions on statistical correlations with an IQ test that may or may not be a valid measure of intelligence is highly questionable. Worse still, is doing this using statistical correlations from meta-analysis of cherry-picked studies and data.
The story told here is all too common today in how government scientists and policymakers develop and implement new guidelines for water, and too credulous media report it uncritically.
They intentionally omit key facts and evidence in their science reviews. They purposely baffle us with dubious claims to create a false impression of the severity of an environmental or public health issue.
Then they invoke “precautionary-based” arguments (i.e., no known dose-response threshold) to propose policies and guidelines whose benefits are essentially unprovable.
Send it to the journalistic horde, mix in a bit of investigative reporting, and presto… a fake crisis is made!