Surely many of you remember that movie in which Julia Roberts embodies the role of Erin Brockovich as an administrative buffet of lawyers, and ends up winning a case of millions of dollars against a large company. This company, in one of its facilities had led to leaks, which had poisoned a nearby aquifer, and caused cancer among hundreds of people.
Well, what if I told you that possibly Erin Brockovich was not rightAnd that there really was never or could not prove a causal relationship between chemical spills, and cancer?
Case groupings and randomness
One of the most complicated things in any scientific study is to separate the grain from the straw. And speaking in terms that science, mathematics uses, this translates into determining if something we are observing is by chance or if there really is a relationship between two or more factors.
Achieving discrimination is very complex and there are areas of statistics that are dedicated to it. What at first sight can be a direct relationship, in practice does not turn out to be such. In addition, although two factors are positively related, then it remains to be shown that one really causes the other.
In the case of Erin Brockovich, the random variable to be elucidated is whether a group of people in a specific area, with a similar pathology (a cluster or grouping of cases), respond to a possible pollution, like water, or if on the contrary, it is a simple random grouping. It seems that although Erin won the case, getting significant compensation for those affected, science later showed that we were facing the second case.
The case of Erin Brockovich
The company Pacific Gas and Electric (PG&E) from California used Hexavalent chrome (Chrome VI) to prevent corrosion in pipes near a town called Hinkley. For years, appreciable amounts of this compound filtered into the soil, contaminating it and being able to contaminate the aquifers that supplied the population.
Chromium VI is a recognized carcinogen in form inhaled. This is when things start to get interesting.
The case was won because Chromium VI had contaminated the population's water, but it turns out that there is no study on the possible toxicity of Chromium VI when ingested. When inhaled, it has been shown to cause lung cancer and even the precise mechanism is known. In the case of water, no. At least, I have not been able to find studies that prove it for Hinkley concentrations. So much so, that in the USA, there is no maximum contaminant level allowed, and only now has the state of California established such a limit.The real Erin Brockovich
However, Erin's firm won the case, and PG&E had to pay 333 million dollars in compensation, of which more than 100 took the signature itself and Erin won a commission of about 2 million.
The case revisited
Well, it turns out that Hinkley's cluster of cases was pure chance. This was demonstrated by epidemiologist John W. Morgan, who compared the 196 cases of cancer in the area, with other nearby counties, coming to the surprising conclusion that in the case of Hinkley, The number of cancer cases was even lower than the average of nearby counties!.
these 1996-2008 preliminary findings do not identify a generalized cancer excess in the Census Tract encompassing Hinkley, San Bernardino County(source)
That is, Erin Brockovich and his firm, managed to win a historical lawsuit against PG&E for a case in which scientific evidence has failed to prove that:
- Chromium VI, at the levels detected in Hinkley and drunk in the water, were the cause of the cancer that its inhabitants had.
- That the number of cancer cases was abnormally high compared to the average of similar places and populations
What catches my attention in this case is how a small law firm was able to win a case like this, when it seems that science gave the company the reason. I guess it was more profitable to close the case quickly. Of course, the company should have put the means so that Chrome VI had never leaked.