May 28th, 2010
04:22 PM ET

Public health pioneer on trail of "the next lead"

Doctors used to think that lead, like many dangerous substances, was only toxic beyond a certain threshold. That changed thanks to a landmark study by Dr. Philip Landrigan, whose findings inspired a federal ban on lead in paint and gasoline. Today he is a principal investigator with the National Children’s Study, a mammoth undertaking by the National Institutes of Health that aims to follow 100,000 children from before birth to age 21, to identify the health effects of toxic exposures and other factors. He spoke with Dr. Sanjay Gupta.

Dr. Sanjay Gupta: Does it usually start off with a hypothesis on your part? Are you literally thinking, “I think there is a connection between this chemical and this problem?

Dr. Philip Landrigan: I think if you take the long view, it actually usually begins with clinical observation. A doctor somewhere who's smart and astute observes that the children who are exposed to a particular chemical are having problems. That's what happened 100 years ago when childhood lead poisoning was first recognized, in Australia. It's what happened 50 years ago when methyl-mercury poisoning was first recognized in Japan, at a village called Minamata. These were situations of acute, high-dose exposure, and smart clinicians recognized the connection between the exposure and the disease. Sometimes a lot of detective work was involved. Once the connection is established by an astute clinician, then hypothesis become part of the story. A number of years ago, we said, “We know that high-dose exposure causes devastating injury to the brain, with coma, with convulsions, with various, very severe clinical manifestations. Might it not be possible that a lower dose also causes dysfunction?” But that dysfunction requires more specialized testing to recognize.

Gupta: When you're talking about cause and effect, are there things now that in 10 to 20 years, kids will come to us and say, “When did you first start to suspect that X was a problem?” Are there things right now that in the back of your mind where you're thinking, “I can't prove this yet, but I'm pretty convinced that this it's going to be a problem and it's causing [problems] in kids?

Landrigan: Well I think one very important class of chemicals that falls squarely in that category today are the phthalates. Phthalates are a type of chemical that falls under the broad category of plastics chemicals. They're added to a lot of rigid plastics, like polyvinyl chloride, to make them flexible. Other phthalates are widely used in cosmetics, skin creams and the like, and they penetrate into people's bodies through the skin. Investigators in our department at Mount Sinai School of Medicine of New York have just recently published a paper in one of the peer reviewed medical journals, which showed that babies who were exposed in the womb to phthalates – six or seven years ago – are now, at age seven, showing aberrations in behavior that look very much like attention deficit disorder. This is obviously something that has to be corroborated; this is just one study. But we're all exposed to phthalates, and if this finding holds up, we've got a problem that we've got to do something about.

Gupta: What is the reaction to the sort of work that you do, within the medical community?

Landrigan: I think there's growing appreciation for this work. You know, historically, most medical students have had very little training in environmental medicine. The average is about four or five hours, in most medical schools across the country. And so most doctors know about lead poisoning; most doctors know about the environmental triggers of asthma, but beyond that their knowledge base is a little thin, and often they don't have much appreciation for environmental problems.

For more of Dr. Gupta’s conversation with Dr. Landrigan, watch “Sanjay Gupta, MD,” Saturday and Sunday at 7:30 a.m., ET.

soundoff (12 Responses)
  1. Gregory Wagner

    Really lead is not used too often in products. The main focus is on ore plants that send lead dust into the air and Chins made products.

    -Gregory Wagner

    May 29, 2010 at 23:02 | Report abuse | Reply
  2. TONI W.


    May 30, 2010 at 08:03 | Report abuse | Reply
  3. Tom Hennessy

    Dr. Landrigan speaks of OTHERS and THEIR lack of knowledge of 'environmental medicine' WHEN in fact HE has very little more knowledge than they. Dr. Landrigan attempts to ELEVATE lead poisoning to some position of 'possible problems' WHEN the metal IRON has been shown to be involved in MORE diseases than any other metal INCLUDING lead. The TARGETING of iron is now recommended in more diseases than ANY other metal in history. Believe it or not.
    Man is a herbivore.

    May 30, 2010 at 09:11 | Report abuse | Reply
  4. May H

    To Toni W: Lead stays in the system for a long, long time. It becomes incorporated in the bone, and can be released by the bones for 20-30 years after exposure, and of course there are the demonstrated irreversible neurotoxic effects, as well as cardiovascular and gastrointestinal effects . Its effects are widespread and insidious throughout the body (even people with high levels at first will seem normal, but then decompensate over time), and there is no safe threshold for exposure. If you were exposed to lead in your work, you should also have your children tested, if you have any, as lead dust can be carried on your clothes back to home and contaminate the environment there as well.

    June 1, 2010 at 16:02 | Report abuse | Reply
  5. Rich T

    Numerous scientific studies have shown that phthalate levels in products are safe. Statistical studies and observations (like the ones mentioned above by Landrigan) can be useful for determining where more research may be needed, but do not demonstrate harm. Phthalates have been studied by various regulatory agencies and have concluded they are safe. It is also important to make distinctions among phthalates. The phthalates used in plastics differ from the phthalates used in cosmetics. DINP, a common phthalate found in flexible plastics, has been thoroughly evaluated and proven to be safe by government bodies like the Consumer Product Safety Commission and the Center for Disease Control. Although it is always prudent to be cautious about chemicals, it is also important to consider the risks introduced by precautionary actions such as replacing the chemical of concern with an alternative. Restricting the use of tested chemicals proven to be safe opens the risk of exposure to less studied substances that have unknown effects.

    June 2, 2010 at 11:13 | Report abuse | Reply
  6. toniw

    well mr. science guy..i know i used lead solder. i can read. if you were not going to answer my question... then why reply? i also read the interview and if i remember right it was about lead...so now mr. science guy what is your opinon on string theory?

    June 4, 2010 at 11:21 | Report abuse | Reply
  7. toniw

    To Mayw...thank you so much for you reply..unlike mr. science guy...you answered my question. i do have two children and two grandchildren. i did not even think about it being on my clothes...thank you so much.

    June 4, 2010 at 11:28 | Report abuse | Reply
  8. Matthew

    Phthalates are everywhere, suggesting we all have regular exposure and probably retain some in our bodies. The question is how do we get rid of it and would a weight loss program suddenly bring "stored phthalates" into our blood stream in large amounts?

    June 7, 2010 at 00:59 | Report abuse | Reply
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.