A recent study in the March issue of the journal Pediatrics [vol. 127(3): e693-e700] reports on a correlation between pre-natal exposure to the common synergist piperonyl butoxide (PBO) and delayed mental development among 3 year-old children. In a review of the article, e! Science News reported the author as saying that the drop in IQ points [among children whose mothers had higher PBO exposure] is similar to that observed in response to lead exposure. Megan Horton, of the Mailman School of Public Health and lead researcher, said the drop, while not severe enough to affect a child's overall function "...is educationally meaningful..." Going a little further out on a limb, she added that it "...could shift the distribution of children in the society who would be in need of early intervention services".
The results of this study should be considered preliminary, and certainly indicate the need for more research. Similar to the study on ADHD that I reported on last year, the data shows a correlation, but does not indicate a cause and effect relationship. Further studies may or may not substantiate the correlation. Furthermore, the authors note that this is the first study to ever look at the health effects of PBO on humans (previous studies, presumably having been done only on laboratory animals).
The paper brings up an interesting issue with regard to the pest control industry. What criteria should we use to make decisions about the kinds of pesticides we use in our business? Should a new study impact the way we use chemicals? Or should we always just follow the lead of the EPA when it permits or restricts use of a pesticide?
Ultimately, and from a legal point of view, the EPA is our guide. The EPA has hundreds of toxicologists trained to look at studies such as these and determine whether there is enough data to justify a change in label requirements. However, the process of revoking a use, or a pesticide, can take years.
The biggest question I had about this study concerned the mothers' exposure to PBO. Piperonyl butoxide in itself is not toxic to insects. Rather, it is added to a few insecticides--most notably pyrethrins--to prevent insects from detoxifying the actual insecticide. It turns out that pyrethrins, by themselves, are great at quickly knocking down, but not killing, most insects. Adding PBO to pyrethrins merely keeps insects down for the count.
Most pyrethrins formulations, including a number of over the counter (OTC) consumer products, contain PBO in low concentrations--usually less than 5%. In recent years, however, some professional products have included higher percentages of PBO (e.g., 60%). I've never fully understood the reason for the popularity of this mixture, given that PBO is non-insecticidal and that only small amounts of it are needed to synergize pyrethrins. From what I can gather informally, PBO mixtures are being used increasingly by frustrated PMPs for bed bugs. But I've always been under the impression that only a small percentage of residential pesticide applications by professionals used PBO. It was surprising to me therefore to read that PBO was detected in 75% of personal air samples collected in the study.
The study assumes PBO was used as a synergist with permethrin; however, permethrin is not normally sold with PBO. Unless a lot of New York PMPs are using this combination (perhaps in bed bug applications?) I am skeptical that this use pattern is common throughout the country. It's also possible that the PBO is coming from use of OTC products by the householders themselves. Or there might be some non-pest control source of PBO. In any case, it seems like one of the first regulatory steps would be to find out where PBO exposure is coming from. [Any insights in this regard from readers would be welcome!]
In the meantime, in my opinion it would be prudent to consider limiting use of products with high percentages of PBO in accounts with pregnant women or infants. I'm not convinced yet that PBO is posing a health risk to the unborn or very young; but in most cases there are good alternatives. Our industry should be placing highest value on customer safety, so why don't we take a proactive lead on this one?
Showing posts with label toxicology. Show all posts
Showing posts with label toxicology. Show all posts
Tuesday, February 15, 2011
Tuesday, August 12, 2008
Risks and pesticides
I was reading a new product label this morning and came across a phrase that caught my attention. The label stated that "It is impossible to eliminate all risks inherentlyassociated with the use of this product."
This phrase, undoubtedly drafted by a lawyer and--I suspect--ignored by most users of the product, reminded me of a profound principles of pesticide toxicology and safety testing--one that I think few of us fully understand or appreciate: "It's impossible to prove that a pesticide is absolutely safe."
Science is a wonderful process. It allows us to discover useful things about our world. It forms the basis for new technology, answers our deepest questions about the universe, and brings wonder into our lives. Science, however, has it's limits. One of its limits is that it cannot prove absence of harm with complete certainty. It's the old "you can't prove a negative" argument.
Let me give an example. If my job is to test the safety of a new pesticide, I may expose a variety of organisms to my product to see if anything bad happens. Toxicologists routinely do this in laboratories with mice and rats and bacteria. Some tests are designed to measure acute toxicity, others look for evidence of mutations, others for cancer or other chronic disease. Suppose in the course of my testing all the rats develop cancer. This would be alarming evidence that my pesticide might be a human carcinogen. Evidence is strengthened if there are epidemiological studies that show a pattern of elevated cancer rates in humans exposed to the pesticide during its manufacture or use.
Now suppose there are no signs of cancer or other illness in my animals. Have I proved that my pesticide is safe? No. Science, because of physical and economic limitations, cannot prove safety with absolute certainty. For example, pesticide toxicology studies are not generally performed on people for ethical reasons. And people, despite our many occasional similarities, are not rats. Also, we cannot rule out all possible genetic, environmental or health factors that might influence carcinogenicity.
We know of cases, for example, where pesticides have proved exceptionally toxic to people taking certain prescription drugs. In these cases the drugs interfered with the user's ability to detoxify the pesticides, making them more toxic.
If we insisted that science provide absolute proof of safety, the science would become almost infinitely expensive. The best we can do is require a robust set of testing requirements, and base our decisions on the best available science. In addition, there should be a system of reporting suspicious patterns of health complaints associated with pesticide manufacture and use.
This is exactly what we do in the United States. The U.S. has, arguably, one of the best pesticide registration and approval processes in the world. New pesticides are incredibly expensive to register, in large part because of the safety testing required by the U.S. Environmental Protection Agency. The biggest beneficiaries of this regulatory process are those of us who work with pesticides on a daily basis.
So what's a pesticide applicator to do? Follow the label. The answer is so obvious that we often forget to do it. Labels are written to provide wise protection from the admitted limitations of our science when it comes to safety testing. From the precautionary statements, to the requirements for protective clothing, pesticide labels provide uncertainty protection.
Though they can be extremely uncomfortable in heat (especially in our part of the country), gloves, respirators and chemical resistant clothing, when required on the label, are essential to our safety. It may be necessary to explain this to a customer who balks at an applicator wearing gloves or breathing filters. They can be told that the extra protection is required by law (the label is the law) because, unlike them, applicators are exposed on a daily basis to our pesticide tools. It's not an admission of toxicity; it's a common sense precaution. It's an acknowledgement that we don't take unecessary chances with ours or our customer's health.
We should remember that there will always be risks working with pesticides, as with nearly any other consumer chemical product. That's the surprisingly wise message of the pesticide label.
This phrase, undoubtedly drafted by a lawyer and--I suspect--ignored by most users of the product, reminded me of a profound principles of pesticide toxicology and safety testing--one that I think few of us fully understand or appreciate: "It's impossible to prove that a pesticide is absolutely safe."
Science is a wonderful process. It allows us to discover useful things about our world. It forms the basis for new technology, answers our deepest questions about the universe, and brings wonder into our lives. Science, however, has it's limits. One of its limits is that it cannot prove absence of harm with complete certainty. It's the old "you can't prove a negative" argument.
Let me give an example. If my job is to test the safety of a new pesticide, I may expose a variety of organisms to my product to see if anything bad happens. Toxicologists routinely do this in laboratories with mice and rats and bacteria. Some tests are designed to measure acute toxicity, others look for evidence of mutations, others for cancer or other chronic disease. Suppose in the course of my testing all the rats develop cancer. This would be alarming evidence that my pesticide might be a human carcinogen. Evidence is strengthened if there are epidemiological studies that show a pattern of elevated cancer rates in humans exposed to the pesticide during its manufacture or use.
Now suppose there are no signs of cancer or other illness in my animals. Have I proved that my pesticide is safe? No. Science, because of physical and economic limitations, cannot prove safety with absolute certainty. For example, pesticide toxicology studies are not generally performed on people for ethical reasons. And people, despite our many occasional similarities, are not rats. Also, we cannot rule out all possible genetic, environmental or health factors that might influence carcinogenicity.
We know of cases, for example, where pesticides have proved exceptionally toxic to people taking certain prescription drugs. In these cases the drugs interfered with the user's ability to detoxify the pesticides, making them more toxic.
If we insisted that science provide absolute proof of safety, the science would become almost infinitely expensive. The best we can do is require a robust set of testing requirements, and base our decisions on the best available science. In addition, there should be a system of reporting suspicious patterns of health complaints associated with pesticide manufacture and use.
This is exactly what we do in the United States. The U.S. has, arguably, one of the best pesticide registration and approval processes in the world. New pesticides are incredibly expensive to register, in large part because of the safety testing required by the U.S. Environmental Protection Agency. The biggest beneficiaries of this regulatory process are those of us who work with pesticides on a daily basis.
So what's a pesticide applicator to do? Follow the label. The answer is so obvious that we often forget to do it. Labels are written to provide wise protection from the admitted limitations of our science when it comes to safety testing. From the precautionary statements, to the requirements for protective clothing, pesticide labels provide uncertainty protection.
Though they can be extremely uncomfortable in heat (especially in our part of the country), gloves, respirators and chemical resistant clothing, when required on the label, are essential to our safety. It may be necessary to explain this to a customer who balks at an applicator wearing gloves or breathing filters. They can be told that the extra protection is required by law (the label is the law) because, unlike them, applicators are exposed on a daily basis to our pesticide tools. It's not an admission of toxicity; it's a common sense precaution. It's an acknowledgement that we don't take unecessary chances with ours or our customer's health.
We should remember that there will always be risks working with pesticides, as with nearly any other consumer chemical product. That's the surprisingly wise message of the pesticide label.
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