{"id":13125,"date":"2018-08-04T02:11:08","date_gmt":"2018-08-04T02:11:08","guid":{"rendered":"http:\/\/www.lifeandnews.com\/articles\/?p=13125"},"modified":"2018-08-05T02:15:51","modified_gmt":"2018-08-05T02:15:51","slug":"does-monsantos-roundup-cause-cancer-trial-highlights-the-difficulty-of-proving-a-link","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/does-monsantos-roundup-cause-cancer-trial-highlights-the-difficulty-of-proving-a-link\/","title":{"rendered":"Does Monsanto’s Roundup cause cancer? Trial highlights the difficulty of proving a link"},"content":{"rendered":"

Richard G. “Bugs” Stevens<\/a>, University of Connecticut<\/a><\/em><\/span><\/p>\n

Does glyphosate, the active ingredient in the widely used weedkiller Roundup, cause non-Hodgkin lymphoma<\/a>? This question is at issue now in a lawsuit in San Francisco Superior Court<\/a>. Hundreds more claims have been cleared to proceed in a federal multi-district lawsuit<\/a>.<\/p>\n

Much of this litigation is based on a 2015 determination by the International Agency for Research on Cancer<\/a>, part of the World Health Organization, that glyphosate is a probable human carcinogen<\/a>. This report has come under heavy criticism<\/a>, which is not surprising because there\u2019s a lot of money at stake.<\/p>\n

The IARC classification relied in part on experiments in mice. But is that enough to conclude the weed killer causes cancer in humans? Mice are not people<\/a>, so probably not.<\/p>\n

If it was simple to determine the cause of cancer in humans, scientists would do the right experiment and we\u2019d know the answer pretty quickly.<\/p>\n

But it\u2019s not simple. <\/p>\n

Proving causation in product liability lawsuits<\/h2>\n

Epidemiology is one of the sciences that provides evidence needed to prove cause and effect in medicine and public health. It is the most important tool for determining whether exposure to a given substance increases the risk of disease. The problem is that it is easy to do it badly, and a bad study is worse than no study at all. <\/p>\n

In fact, after a special hearing examining the science on both sides of the glyphosate argument, U.S. District Judge Vince Chhabria called epidemiology \u201cloosey-goosey\u201d and a \u201chighly subjective field.\u201d<\/a> Nonetheless, he concluded that the views on both sides were reasonable and should be heard in court, with the verdict up to a jury.<\/p>\n

\n \"\"<\/a>
\n Illinois corn farmer Jerry McCulley sprays glyphosate across his cornfield in Auburn, June 1, 2010.<\/span>
\n AP Photo\/Seth Perlman<\/a><\/span>
\n <\/figcaption><\/figure>\n

I have spent much of my working life trying to help figure out why people get cancer<\/a>. To illustrate how hard it is to prove causality, consider the question: Does smoking cause lung cancer?<\/p>\n

Innumerable epidemiological studies since the 1940s have shown a strong association between smoking and lung cancer. But there has never been a randomized trial in humans<\/a>. In addition, we know from experimental studies that smoking rats don\u2019t get lung cancer<\/a>. <\/p>\n

For years, Big Tobacco dismissed observational studies in people (epidemiology) with the mantra that \u201cassociation is not causation,\u201d and avoided regulation. The scientific community was intimidated by this strategy for far too long. Eventually, the studies accumulated to the point that the association was overwhelming, and cause and effect could not be denied.<\/p>\n

There are two main types of epidemiological study designs: cohort and case-control. In a cohort study, a large group of people \u2013 some smokers, some not \u2013 are followed over the years to see who gets sick. In a case-control study, a group of lung cancer patients (perhaps several hundred) are asked about their smoking history, along with an equal number of people without lung cancer.<\/p>\n

Invariably, in cohort study after cohort study, smokers got sicker from heart disease, lung cancer and many other maladies over time. In most of these studies, scientists did their best to take account of other differences between smokers and non-smokers, so as to isolate the effect of smoking. Also invariably, in case-control studies patients with lung cancer were much more likely to have been smokers than people in the general population.<\/p>\n

\n