Environment
Urgent action needed on dioxins, says toxicologist
The environmental scientist whose work on dioxins last year prompted governments around the world to suspend the use of some pesticides says there is more to the problem and authorities need to act urgently.
Although dioxins have been banned from the ingredients of pesticides in Australia for more than a decade, many dioxins emerged in the manufacturing process and there was no end-stage monitoring to protect consumers and the public, said University of Queensland scientist Dr Caroline Gaus.
Numerous environmental and health issues were associated with undeclared dioxin impurities, said Dr Gaus, an environmental toxicologist with the National Research Institute for Environmental Toxicology (ENTOX).
Little information was available about the impurities because they were created during the production process so were not original ingredients.
“We estimate that the amount of these impurities is relatively high compared to other current dioxin sources, but this cannot be adequately quantified due to the commercial protection of data on pesticides use in Australia and internationally,” Dr Gaus said.
She said pesticides with impurities used in high volumes represented a previously neglected but significant and concerning source of dioxins in the environment. They also posed a risk to the health of people handling pesticides, and to consumers.
“Some of these pesticides contained high concentrations of dioxins, comparable to those known from pesticides which are banned or restricted for use in most countries since the 1980s and 90s,” she said.
Dioxins are linked to a range of cancers and are considered one of the most toxic man-made chemicals. They can cause adverse health effects in humans and wildlife including cancer, and act on development, reproduction and the endocrine system.
Research by Dr Gaus and PhD student Eva Holt last year showed that a wide range of currently used and globally marketed pesticides contained dioxin impurities, despite the widespread belief that modern pesticides were no longer a significant dioxin source.
As a result of their work, a new wave of suspensions, recalls, restrictions and government reviews on pesticide formulations is under way worldwide, including in the United States, Canada, New Zealand and Australia.
The study analysed 23 different pesticide formulations, containing 15 different active ingredients currently used in Australia (plus four formulations that are no longer registered for use in Australia), including insecticides, herbicides and fungicides. Dioxins were detected in all samples, including some commonly used products. Researchers estimate approximately 200 pesticides have the potential to contain dioxins.
The pesticides are used on crops including cotton, potatoes, lettuce, tomatoes, beans and peanuts, as well as in parks and recreation areas, at turf farms and plant nurseries.
“In view of the global manufacturing, distribution and use of pesticides, international regulation and monitoring strategies should be developed and implemented to identify, evaluate, and target pesticide dioxin sources at the manufacturing stage,” Dr Gaus said.
Some Recent Restrictions
The Australian Pesticides and Veterinary Medicines Authority (APVMA) suspended all formulations containing quintozene (pentachloronitrobenzene) from use in April this year due to risk to workers applying the pesticide, which was commonly used on golf courses. The fungicide is under review in New Zealand where it is used on bulbs and turf. The manufacturer recently initiated a voluntary recall of product containing quintozene. The APVMA has recently suspended the pesticide PCNB from sale and a stop sale order has been issued by the US Environmental Protection Agency.
About Dioxins
• Dioxins are toxic compounds which have adverse health effects in humans and wildlife. They can elicit adverse health effects at low levels (cancer, immunotoxicity, reproduction, endocrine function, development).
• These toxicants are managed under the international Stockholm Convention treaty which aims to protect human health and the environment by reducing and eliminating dioxin release to the environment. More than 150 countries, including Australia, have ratified the Stockholm Convention treaty since 2004.
• Most chlorinated pesticides have the potential to contain dioxins if manufactured under certain conditions and processes (e.g. > 150 ºC, alkaline conditions, process including chlorine) – the US EPA lists 161 chemicals (but it is not complete – PCNB for example is not listed). Thus, pesticides were considered historical sources of dioxins and contemporary monitoring data in most current-use pesticides are lacking.
• Dioxin impurities can vary between manufacturing facility, batch, year and country due to variations in production processes and conditions.
About the Research
• 23 different formulations containing 15 different active ingredients currently used in Australia (plus 4 formulations that are no longer registered for use in Australia), including insecticides, herbicides and fungicides, were analysed. Dioxins were detected in all samples. These include commonly used pesticides, such as PCNB, MCPA, 2,4-D, chlorothalonil and triclopyr/picloram. Others are Fluroxypyr, Mecoprop, Flumetsulam, Imazamox, Prochloraz, Fenamisphos, Chlorpyrifos, Lindane; 2,4-D; 2,4-DB; Chlorthal amd Quintozene.
• Some of these pesticide formulations contained high concentrations of dioxins, comparable to those known from pesticides which are banned or restricted for use in most countries since the 1980/90s.
•Highest dioxin (1,100-2,000 mg/tonne AI) and TEQ (2,400-5,700 µg/tonne AI) concentrations were found in the fungicide quintozene (also known as pentachloronitrobenzene (PCNB)).
• Dioxin concentrations in PCNB are comparable to those known from the banned pesticides 2,4,5-T (trichlorophenoxyacetic acid; the key ingredient of Agent Orange). Note: TEQ concentrations in PCNB are at the lower end for those known for 2,4,5-T (approaching the 7,000 µg/tonne used under the Stockholm Convention to estimate historical dioxin releases via past use of 2,4,5-T).
• There are about 6000 pesticide products on the market in Australia (containing ~2000 different active ingredients) – the UQ/ENTOX scientists analysed only a small proportion (0.4 per cent) of these.
• Dioxin concentrations in other pesticides analysed ranged from 61-190 ug TEQ/tonne AI. Impurity concentrations may vary considerably depending on the conditions employed during pesticide production and should therefore be monitored regularly.
• As many pesticides are used in high volumes, they can represent previously neglected but important sources of dioxins to the environment and pose a risk to the health of people handling pesticides.
• Based on these findings, the APVMA have recently suspended the pesticide PCNB, due to dioxin contamination and the associated risks to pesticide applicators. Similarly, the US EPA have issued a stop sale order for PCNB.
• The estimated release of dioxins from the use of PCNB is 27 g TEQ/year (10-90th percentile range: 14-110 g TEQ/year). The dioxin release from this pesticide alone ranks among the top 5 dioxin sources to land in Australia (range 28-110 g TEQ/year).
• The greatest source of uncertainty with these estimates is the lack of information on pesticide use volumes in Australia, which is commercial in confidence and thus not publicly available. This is why the dioxin release associated with many of the pesticides analysed by the UQ/ENTOX scientists could not be estimated to date (has to be modelled)
• The cumulative dioxin release associated with high volume-use of different pesticides may be an important source of dioxins, even if pesticides contain lower dioxin levels than PCNB, e.g. if all pesticide products were contaminated at levels ranging from 100-10,000 µg TEQ/tonne AI and used at a total of 200,000 tonnes per year, then the annual dioxin release would be between 20 and 2000 g TEQ/year.
Note: data on the amount of pesticides used in Australia is not publicly available (commercial in confidence), total pesticide use may be considerably higher than 200,000 tonnes (approximately 2.25 million tonnes of pesticides a year are used in the USA, including 1.18 million tonnes per year of chlorine and hypochlorite pesticides).
The study was funded by an Australian Research Council Discovery Grant and undertaken by the National Research Institute for Environmental Toxicology, University of Queensland (Eva Holt, Caroline Gaus) in collaboration with the National Measurement Institute in Sydney (Gavin Stevenson) and collaborators from Germany (Roland Weber).
The United Nations Environmental Protection Agency has used the data from the study to develop a burden of toxicology measure for use worldwide. It helps identify and prioritise dioxin sources.
• Babies & Pregnancy
Toxic chemicals in pregnant women? A Q&A with Sarah Janssen
Dr. Sarah Janssen looks at why 163 chemicals are in the bodies of pregnant women.
By SimpleSteps.orgMon, Feb 07 2011 at 3:10 PM EST Comments
This January, a study by the University of California San Francisco confirmed that pregnant women carry multiple chemicals in their bodies that can be passed onto their fetus. Published in Environmental Health Perspectives, the study evaluated data collected by the U.S. Centers for Disease Control and Prevention in 2003-2004. Overall, 43 banned as well as currently used chemicals — including PCBs, organochlorine pesticides, PFCs, phenols, PBDE flame retardants, phthalates — were detected in 99-100% of over 250 pregnant women.
Though we have known for many years that humans are contaminated with dozens of chemicals from birth until late in life, this study marks the first time the number of chemicals in pregnant women has been counted. Many of the 163 chemicals studied are known to be transferred to the fetus and have been linked to poor health outcomes, placing them at risk for birth defects or chronic illnesses later in life. Some of the chemicals detected — such as PCBs — have been banned for over 30 years.
This study adds to the weight of evidence that fetuses are exposed to a soup of chemicals during vulnerable periods of development. Furthermore, because the women in the study were tested for exposure to only a fraction of chemicals on the market, it also suggests that pregnant women are likely carrying and passing onto their fetuses many more chemicals than have been reported here. Catherine Zandonella spoke with NRDC senior scientist Sarah Janssen, MD, PhD, MPH, about the implications for women and their children.
SimpleSteps: What are the possible harmful health effects to a child who was exposed in the womb to these chemicals during pregnancy?
Dr. Sarah Jansenn: Over the past several decades, scientists have discovered that exposures occurring early in life, either in the womb or during early stages of childhood development, can cause harm that doesn’t occur when the exposure happens later in life. This is because during fetal, neonatal and early childhood the body is rapidly growing and developing under a carefully orchestrated process that is dependent on stepwise events.
When one of those events is interrupted, the next event is disrupted and so on until permanent and irreversible changes can result. This could result in a very subtle effect — like an alteration in how the brain develops resulting in changes in attention span, learning ability, or behavioral changes. Or it could result in other impacts like altering where fat cells are deposited in the body or modifying the development of an organ predisposing it to cancer later in life.
Many of these types of studies have been done in laboratory animals, but we do have some evidence gestational exposures are causing human harm. For example, lead, mercury and PCBs have all been shown to harm the developing brain resulting in a loss of IQ points, impaired learning and memory, and behavioral changes.
SimpleSteps: Can nursing infants be exposed to these chemicals, if so, and what harm might result from breastfeeding?
Yes, some of these chemicals are found in breast milk. It is frustrating and maddening that a baby’s first food is contaminated with industrial chemicals, but breast milk remains the best form of nutrition for infants.
The benefits of breast feeding outweigh any of the risks — including exposure to chemicals. We have information about the benefits to mom and baby on our website.
In addition, there have been some studies that have shown breast feeding can counter some of the harmful effects often seen after exposure to PCBs in the womb. Bottom line is that while we work to eliminate the most harmful chemicals from our breast milk — breast remains best!
SimpleSteps: Can fetal exposure to chemicals in the womb cause problems with fertility and reproduction later in life?
Yes, it is likely. Because gametes — the cells that form sperm and eggs — are formed in fetal life and reproductive organs are also forming throughout gestation, exposures to chemicals during this time can permanently alter these structures and result in infertility that isn’t manifest until several decades later.
For example, from animal studies we know that exposure to phthalates during fetal development can result in malformed genitals, poor sperm quality and even testicular cancer. Preliminary studies in humans have linked phthalate exposure during fetal development to a feminization of the genitals, though it isn’t yet known whether this results in reproductive harm.
SimpleSteps: So you are telling me that these chemicals can harm the children of exposed pregnant women. Do these chemicals harm the women also? How?
For most industrial chemicals, we have very limited information on their effect on adults. There are some studies that have shown that bisphenol A (or BPA) may promote the growth of aggressive breast tumors and also may interfere with chemotherapy treatments. Recently published research has found women with polycystic ovarian syndrome also have higher levels of BPA. Phthalates have been linked to poor sperm quality in adult men.
By far, the most information we have is on exposures during early development but we must remember that there are other life stages that are also vulnerable, including puberty, pregnancy, lactation and menopause. Most research has focused on earlier life stages. We need more research on the other vulnerable periods of development.
SimpleSteps: Aren’t the levels of the chemicals detected in the study very small? How do we know that these tiny amounts can cause harm to a developing fetus?
Yes, the levels of chemicals found in the bodies of these pregnant women were very small. Many of them are in the parts-per-billion range, which is analogous to a teaspoon of water in an Olympic size swimming pool. This may not seem like a very large amount, but it is important to remember that the profound physical, emotional and behavioral changes that occur during puberty are the result of a spike in sex hormone levels in the parts-per-billion or even parts-per-trillion range. So small amounts of a chemical exposure could be significant, especially if they interfere with your body’s hormones.
I don’t agree with the view that, unless EPA or the public can prove that hundreds of chemicals in our bodies cause harm, we can safely assume they are not a problem. Toxic chemicals — carcinogens, endocrine disrupters, neurotoxicants like those found in the bodies of pregnant women in this study — are a problem, which is why we should be reducing exposure and identifying safer substitutes as much as possible.
SimpleSteps: Aren’t people living longer and rates of cancer going down?
Overall deaths from cancer are going down, largely due to the decrease in smoking, and because early cancer detection and treatment has improved. We have more cancer survivors and that is a great accomplishment, but the incidence of a number of cancers have continued to rise or have remained steady, including thyroid, liver, kidney and children’s brain cancer and children’s leukemia. Many of these cancers have been linked to chemical exposures.
SimpleSteps: Do these chemicals stay in bodies forever, or at least for long periods of time?
Chemicals like BPA and phthalates are broken down by the body relatively rapidly, within a couple of days, and excreted. However, the fact that we can so consistently measure these chemicals in humans means that we are taking them in as fast as our bodies can get rid of them, so there is a more or less constant level of exposure.
Other chemicals that are more persistent, accumulate in fat and resist breakdown are more long-lived in our bodies. These are chemicals like PCBs, flame retardants like PBDEs, and heavy metals like mercury and lead. Some of these chemicals can reside in our bodies for decades, which is why this study found so many chemicals that have been banned for many years.
SimpleSteps: How are people exposed? Through dust? Ingesting leaching chemicals? Direct contact?
The route of exposure really is chemical- and situation-specific. For example, for most people BPA exposure occurs from food. However, BPA is used in many other places including thermal paper receipts, and cashiers who handle these receipts have been found to have higher BPA exposures, presumably because it is absorbed across their skin.
BPA is also used in medical devices and other studies have found that infants in the neonatal ICU have high levels of exposure, presumably because BPA is leaching from the devices into their bodies.
Many other chemicals have been found in dust, which can be ingested or inhaled especially by infants and toddlers who spend most of their time on the floor picking up things and putting them in their mouths. Flame retardants and phthalates are examples of two groups of chemicals that have been found to accumulate in dust.
SimpleSteps: What is the evidence that exposure to mixtures of chemicals could pose greater risks in combination than they would individually?
Mixtures of phthalates and other hormone-disrupting chemicals including some pesticides have been found to have additive effects such that exposures to the individual chemicals at doses shown to cause no harm have been found to cause harm when combined in a mixture.
Furthermore, there are a number of environmental chemicals which mimic thyroid hormone and also can be expected to exert additive or synergistic effects when combined in a mixture. Chemicals that interfere with normal development and function of the brain such as lead, mercury and PCBs — which were all detected in this study of pregnant women — could act together to collectively result in a greater decline in mental capacity than any one chemical alone.
The National Academy of Sciences (NAS) recently issued a report underscoring the importance of evaluating groups of chemicals that cause the same adverse outcome, such as neurodevelopmental harm caused by thyroid hormone disrupting chemicals. The NAS stated that basing chemical safety evaluations on just one chemical at a time or ignoring other modes of action that contribute to the same outcome “may lead to considerable underestimation of risks to the developing fetus.”
If these chemicals are so bad for us, then why do our federal laws allow pregnant women to be exposed to them?
Unfortunately, the federal law that governs exposure to most industrial chemicals is broken. Unlike the other landmark environmental laws passed in the mid-1970s, the Toxic Substances Control Act (TSCA) has never been updated and is long overdue for reform.
The law covers some 60,000-plus chemicals that are not pesticides or pharmaceuticals and has been so ineffective that it hasn’t allowed for a full ban of asbestos and has allowed other known toxic chemicals like formaldehyde, phthalates, and heavy metals like lead and mercury to be prevalent in so many of our consumer products.
On top of all that, the flaws in the law have resulted in most chemicals being introduced into the marketplace with little to no information about whether or not they are safe. This unchecked and unregulated use of chemicals has resulted in widespread contamination of our environment and our bodies.
SimpleSteps: For pregnant women and women who are thinking about becoming pregnant, there are many different pieces of advice on things to avoid in order to have a safe and healthy pregnancy. How do you rank this study in terms of how worried women should be about chemical exposures in light of other worries like what foods to avoid, not drinking alcohol or smoking, how much exercise to get, what dietary supplements to take, etc.?
Certainly the amount of information women are bombarded with about what to do and what not to do when getting trying to get pregnant is overwhelming and confusing. There are a lot of things that are in your control — like avoiding alcohol or limiting caffeine intake — and things that may seem out of your control, like avoiding exposure to chemicals that were banned over 30 years ago. It might not seem obvious but there are a lot of overlaps in the sources of exposure to many of these “don’ts” and simple adjustments in behavior can mean that you don’t have to decide which is more important because you can being doing multiple good things with one action. For example, many of the now banned chemicals which were found in the pregnant women in this study are found in animal fat. So eating a low fat diet is not only a healthy nutrition choice but also reduces exposure to these toxic chemicals.
Here are six easy and important ways to reduce exposures:
1. Leave your shoes at the door — pesticides and other outdoor contaminants can find their way into your home by being tracked in on your shoes.
2. Avoid “antibacterial” products — plain soap and water does the job of getting rid of “germs” and use of chemicals like triclosan or triclocarban in your soap, toothpaste or other personal care products leads to unnecessary exposure to these hormone disrupting chemicals. Waterless hand sanitizers that contain alcohol are a good and safe alternative when you are away from a sink (see our fact sheet on these chemicals — PDF).
3. Use a damp mop or cloth to dust and use a HEPA filter on your vacuum cleaner — dry dusting, sweeping or using a filterless vacuum cleaner will kick up contaminant laden dust in your home making it easier to breathe in. If you use something damp or a microfiber cloth with a static charge to collect the dust particles you can avoid this.
4. Wash your hands frequently (with plain soap and water). Be sure to wash your hands after dusting or cleaning and after using electronics to wash away any contaminants that might have accumulated on your hands.
5. As much as possible, eat fresh or frozen fruits and vegetables instead of processed or canned food — fresh or frozen fruits and vegetables are less likely to be contaminated with chemicals found in food packaging.
6. Limit your use of strongly fragranced products — cleaning, personal care or other household products. The fragrance often harbors dozens of chemicals that have been linked to harmful health effects.
And for more ways to can minimize exposure, see “9 Steps to a Safer Pregnancy.”
SimpleSteps: How can the public use the information from this study? What can individuals and retailers do? Should this be a call for government action?
Of course, the tips above don’t just apply to pregnant women. But retailers and members of the public should work towards stronger laws that limit the use of chemicals that have never been proven to be safe.
Learn more about the need for TSCA reform at our website: www.takeouttoxics.org and take action by asking the President to act on the recommendations of the 2010 President’s Cancer Panel report, which called for chemical policy reform.
• Exposure to pesticides in womb linked to learning disabilities
By Liz Szabo, USA TODAY
Updated Feb 07, 2011 11:42 AM |
Babies exposed to high levels of pesticides while in the womb may suffer from learning problems, a new study suggests.
The study focused on a chemical called permethrin, one of the pyrethroid pesticides, commonly used in agriculture and to kill termites, fleas and household bugs, says lead author Megan Horton of the Columbia Center for Children’s Environmental Health. Most of the pregnant women in this New York-based study were exposed by spraying for cockroaches.
Permethrin — among the most commonly detected pesticides in homes — is being used more often today as older organophosphorous pesticides are phased out because of concerns that they harm brain development, says Horton, whose study is being published today in Pediatrics.
Researchers measured 348 pregnant women’s exposures by asking them to wear backpack air monitors, Horton says. Researchers followed the women and their children for three years.
Children exposed to the highest pesticide levels before birth were three times as likely to have a mental delay compared to children with lower levels, the study says. Children with the highest prenatal exposures also scored about 4 points lower on an intelligence test, the Bayley Mental Developmental Index. That test has a mean score of 100, with most people’s scores falling within 15 points of that range.
That’s about the same intelligence loss caused by lead, says Philip Landrigan, a pediatrics professor and environmental health expert at New York’s Mount Sinai School of Medicine.
Pyrethroid pesticides kill bugs by “being toxic to the developing brain,” Landrigan says. The results are “very believable and should be taken seriously,” Landrigan says.
Because the study is the first to link permethrin with brain damage, researchers need to conduct additional studies before concluding that the pesticide really harms the brain, says Mary Fox, an assistant professor at John Hopkins’ Bloomberg School of Public Health.
Even without definitive data, however, Fox says it makes sense for pregnant women to reduce their exposure to bug sprays and other pesticides.
To control bugs, for example, she suggests fixing water leaks, keeping food tightly covered and, if necessary, spraying outside instead of inside the home.
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Toxicology. 2007 Jan 18;229(3):194-205. Epub 2006 Oct 29.
Dopaminergic system modulation, behavioral changes, and oxidative stress after neonatal administration of pyrethroids.
Nasuti C, Gabbianelli R, Falcioni ML, Di Stefano A, Sozio P, Cantalamessa F.
Dipartimento di Medicina Sperimentale e Sanità Pubblica, Università di Camerino, Via Scalzino, 62032 Camerino (MC), Italy. cinzia.nasuti@unicam.it
Abstract
Pyrethroids are a class of insecticides involved in different neurological disorders. They cross the blood-brain barrier and exert their effect on dopaminergic system, contributing to the burden of oxidative stress in Parkinson’s disease through several pathways. The aim of the present study was to evaluate the effect of neonatal exposition to permethrin and cypermethrin (1/10 of DL(50)) in rats from the eighth to the fifteenth day of life. Open-field studies showed increased spontaneous locomotor activity in the groups treated with permethrin and the one treated with cypermethrin, while a higher number of center entries and time spent in the center was observed for the cypermethrin-treated group. Lower dopamine and higher homovanillic acid levels were measured in the striatum from both treated groups. A reduction of blood glutathione peroxidase content was measured, while no change in blood superoxide dismutase was observed. Carbonyl group formation increased in striatum, but not in erythrocytes. Lipid peroxidation occurred in erythrocytes, but not in striatum. No changes in fluidity at different depths of plasma membrane were measured in striatum or erythrocytes. The activation of monocyte NADPH oxidase by phorbol esters (PMA) shows that superoxide anion production was reduced in the pyrethroid-treated groups compared to the control group. Our studies suggest that neonatal exposition to permethrin or cypermethrin induces long-lasting effects after developmental exposure giving changes in open-field behaviors, striatal monoamine level, and increased oxidative stress. Although the action of pyrethroids on various target cells is different, a preferential interaction with the extracellular side of plasma membrane proteins can be observed.
• Common insecticide tied to kids’ lower test scores
By Leigh Krietsch Boerner
NEW YORK | Thu Feb 10, 2011 8:46pm EST
NEW YORK (Reuters Health) – Toddlers whose mothers breathed more of a chemical often present in insecticides during pregnancy had slower brain development, according to a study from New York City.
On average, women breathing the highest amounts of piperonyl butoxide, or PBO, had babies who scored 3.9 points lower on a mental development test at age three (85 points and above is considered normal).
These changes are about the same as those seen in kids with low-level lead exposure, according to Megan Horton, a researcher at Columbia University who worked on the study.
“It means that these kids might not do as well in school” later on, said Horton, whose findings appear in the journal Pediatrics.
Baby brains are extra vulnerable to toxic chemicals, because they are not fully formed.
“If you alter the blueprint, there may be lasting long-term consequences,” Horton explained.
She and her colleagues analyzed air samples from a few hundred pregnant women’s environments to track the levels of PBO and another chemical called permethrin. The two compounds are commonly found in bug sprays for indoor use.
Permethrin wasn’t tied to the toddlers’ mental skills. But among the 42 women who breathed the highest levels of PBO — around 4 parts per trillion — nearly half had a baby with a lower-than-normal mental development score.
That compared to only about one in five of women exposed to lower or undetectable levels of PBO. Still, the results don’t prove that PBO in itself causes developmental delays.
Horton said the average amount of PBO in the air is unknown, and that it’s unclear if low levels of PBO are safe.
“For these toxic chemicals, there’s probably no such thing as a safe level during pregnancy,” said Dr. Philip Landrigan, who heads the Children’s Environmental Health Center at the Mount Sinai School of Medicine in New York, and was not involved in the new study.
He suggested that pregnant women who have an insect problem should make sure more bugs can’t get in through measures such as caulking cracks in walls, and that all food is cleaned up.
“Instead of spraying,” he said, “use little baits like roach motels because it’s contained.”
SC Johnson, which makes the PBO-containing Raid bug spray, told Reuters Health they would review the new study.
“All of our products go through an extensive risk assessment,” including possible effects on children and pets, the company added in an e-mail.
SOURCE: bit.ly/gZSdEU Pediatrics, online February 7, 2011.
Addit: Piperonyl butoxide (PBO) is not an insecticide in the traditional sense. It prevents the breakdown of insecticides by blocking several enzymes that oxidize pesticides so that instead of being broken down by the insect (by oxidation), they are not broken down, and therefore are more potent.
The same enzyme class also does numerous other important things such as critical functions in the production of steroid hormones. PBO acts on these enzymes too, and in the same way. So, is it any surprise that a substance that hammers the whole steroid hormone system alters neurological development?
This same enzyme class also affects numerous other important things besides the production of steroid hormones.