Insecticides

For several years, neurologists at UCLA have been building a case that a link exists between pesticides and Parkinson's disease. To date, paraquat, maneb and ziram — common chemicals sprayed in California's Central Valley and elsewhere — have been tied to increases in the disease, not only among farmworkers but in individuals who simply lived or worked near fields and likely inhaled drifting particles. Now, UCLA researchers have discovered a link between Parkinson's and another pesticide, benomyl, whose toxicological effects still linger some 10 years after the chemical was banned by the U.S. Environmental Protection Agency. Even more significantly, the research suggests that the damaging series of events set in motion by benomyl may also occur in people with Parkinson's disease who were never exposed to the pesticide, according to Jeff Bronstein, senior author of the study and a professor of neurology at UCLA, and his colleagues. Benomyl exposure, they say, starts a cascade of cellular events that may lead to Parkinson's. The pesticide prevents an enzyme called ALDH (aldehyde dehydrogenase) from keeping a lid on DOPAL, a toxin that naturally occurs in the brain. When left unchecked by ALDH, DOPAL accumulates, damages neurons and increases an individual's risk of developing Parkinson's.

Het middel imidacloprid wordt steeds vaker in de Noord-Hollandse wateren aangetroffen. Ook wordt steeds vaker de norm voor imidacloprid in de onderzochte oppervlaktewateren overschreden. Imidacloprid wordt in 58% van de meetpunten aangetroffen (in 2011 was dan nog in 52% van de meetpunten). In 10% van de metingen werd de norm overschreden, in 2011 was dit nog maar in 2%. Er is dus sprake van een forse toename van het aantal overschrijdingen. De laatste 5 jaar neemt de sterfte onder bijenvolken wereldwijd sterk toe. Ook in Nederland ligt de bijensterfte de laatste jaren op een niveau van 20-30%, terwijl 10 % sterfte gangbaar is (Bijensterfte in Nederland, 2006 - 2011). De verhoogde doodsoorzaak wordt mede in verband gebracht met de neonicotinoiden. Voor imidacloprid is de zogenaamde ADI (acceptable daily intake), d.w.z. de toelaatbare hoeveelheid die iedere dag door mensen mag worden opgenomen, 0,06 mg per kg lichaamsgewicht. Een mens van 70 kg mag dus dagelijks aan meer dan 4 mg van dit landbouwgif blootstaan. Een recente Japanse studie toonde aan dat neonicotinoiden zoals imidacloprid zich bij zoogdieren precies zo gedragen als nicotine. Nicotine en neonicotinoïde insecticiden gaan een binding aan met nicotinerge acetylcholine receptoren (nAChRs). Deze receptoren zijn betrokken bij cognitieve functies zoals concentratie en geheugen en spelen een belangrijke rol bij de ontwikkeling van het zenuwstelsel, die bij de mens grotendeels voor de geboorte plaats vindt. Blootstelling aan nicotine tijdens de zwangerschap leidt tot een teruggang van volwassen stamcellen en een verandering in de synaptische plasticiteit in de hippocampus van het nageslacht, volgens nieuw onderzoek van de Universiteit van Alabama in Birmingham. Onderzoekers zeggen dat dit een mogelijke oorzaak voor gedragsproblemen kan zijn zoals ADHD (attention-deficit hyperactivity disorder), vaak gezien bij kinderen wiens moeder rookte tijdens de zwangerschap.

Speaking in parliament on Tuesday, Francois Wakenhut, of the commission's environment directorate, said that "multiple causes" were responsible for rising bee mortality and the "collapse" of bee colonies. Calling for measures, he declared, "The clock is ticking and we need to act now." Wakenhut, head of unit for nature conservation and biodiversity, was speaking at a debate on "bee health in Europe", organized by the European bureau for conservation and development and parliament's intergroup on climate change and biodiversity. The official told the packed conference that it was important to stress the importance of insect pollination to the EU economy and general health. He said, "Bees face a disastrous decline in their numbers and there are multiple reasons for this." Several beekeepers attended the event and Peter Maske, president of the German beekeeping association, outlined some of the issues facing the industry. He said there was "clear evidence" that pesticides were a major contributor to bee losses, but another issue which needed addressing was the lack of professional beekeepers in Europe.

The quality and quantity of the data about the risk posed to humans by individual pesticides vary considerably. Unlike obvious birth defects, most developmental effects cannot be seen at birth or even later in life. Instead, brain and nervous system disturbances are expressed in terms of how an individual behaves and functions, which can vary considerably from birth through adulthood. In this article I challenge the protective value of current pesticide risk assessment strategies in light of the vast numbers of pesticides on the market and the vast number of possible target tissues and end points that often differ depending upon timing of exposure. Using the insecticide chlorpyrifos as a model, I reinforce the need for a new approach to determine the safety of all pesticide classes. Because of the uncertainty that will continue to exist about the safety of pesticides, it is apparent that a new regulatory approach to protect human health is needed.

EU agriculture ministers were set to vote on a European Commission proposal to restrict the use of three commonly used neonicotinoid insecticides in Brussels today (Monday, 25/02/13). But the vote has been postponed until 14-15 March. It is not clear why the vote has been delayed. However, it is understood the commission may be seeking to restructure the proposal amid reports that a blocking minority of countries, including Germany, Spain and the UK, had been seeking to derail the vote, citing gaps in the data. In contrast, France, the Netherlands, and Poland support a ban. One industry source told Farmers Weekly: "A number of member states have got concerns about the underlying basis (of the proposal) and it is believed that the commission has met with five or six member states to start looking at alternative proposals that are on the table." Syngenta UK spokesman, Luke Gibbs said the delay offered member states more time to look in detail at what is being proposed. "In our view, the existing proposal put forward by the European Commission is disproportionate and underpinned by a flawed and incomplete technical assessment," he said. Mr Gibbs believes the proposed action would not help bee populations which are being affected by a "wide range of factors". "We believe that a number of member states think similarly and are questioning whether restricting the use of this important tool for farmers would improve long-term outcomes for bee populations," he said. But German Green Party MEP Martin Häusling slammed the commission for the delay and accused the commission of "caving in to the chemical industry".

The residue of imidacloprid in the nectar and pollens of the plants is toxic not only to adult honeybees but also the larvae. Our understanding of the risk of imidacloprid to larvae of the honeybees is still in a very early stage. In this study, the capped-brood, pupation and eclosion rates of the honeybee larvae were recorded after treating them directly in the hive with different dosages of imidacloprid. The brood-capped rates of the larvae decreased significantly when the dosages increased from 24 to 8000 ng/larva. However, there were no significant effects of DMSO or 0.4 ng of imidacloprid per larva on the brood-capped, pupation and eclosion rates. Although the sublethal dosage of imidacloprid had no effect on the eclosion rate, we found that the olfactory associative behavior of the adult bees was impaired if they had been treated with 0.04 ng/larva imidacloprid in the larval stage. These results demonstrate that a sublethal dosage of imidacloprid given to the larvae affects the subsequent associative ability of the adult honeybee workers. Thus, a low dose of imidacloprid may affect the survival condition of the entire colony, even though the larvae survive to adulthood.

I am a retired (Emeritus) scientist with Environment Canada with over 30 years' experience in pesticide evaluation, risk assessment and ecological research. For approximately half of that time, I was the lead regulatory assessor for the risk of pesticides to wildlife in Canada. I have a special interest in the neonicotinoids in that they were of increasing concern to me when I retired less than one year ago. I continue to be involved in pesticide research and assessment as a consultant and have just finished a review of the neonicotinoids from the point of view of their impact on birds.This particular work was commissioned by the American Bird Conservancy. The specific point I wish to make concerns the exchange you were having with the representative of Bayer Crop Science during your 30 January session. Specifically, my comment is about the UK study showing a continuing increase in soil residues, which study Bayer dismissed as irrelevant because it involved a field where straw was reincorporated every year. Bayer's position was that, because straw is a valuable commodity, that study did not follow good agricultural practice and should not be considered. I respectfully submit that your committee missed an opportunity to address the fundamental insight provided by that study, whether or not the study followed usual agricultural practice and whether the price of straw does or does not make this scenario likely in the UK. The issue is that of systemic pesticides more generally. In my opinion, the real question that should have been asked is the following: What are some of the other agricultural conditions where plant material is reincorporated into the soil after taking up neonicotinoid insecticides? Are there other crops with neonicotinoid uses where this happens?

A study published Tuesday points to pesticide use as the single most important indicator of grassland bird declines in the U.S., raising long held concerns over wildlife impacts. Researchers in the UK and Denmark have studied why grassland birds have declined faster than birds in any other biome – many linking declines to pesticide use– but similar research had not been conducted in the U.S. Proposed causes have ranged from: larger fields, the rise of uniform crop monocultures, the loss of native and natural habitat, the increase in autumn sowing and finally, the increase to fertilizer and pesticide inputs. Authors Pierre Mineau, PhD., senior research scientist on pesticide ecotoxicology with Environment Canada, and Melanie Whiteside sought to determine to what extent grassland bird declines were linked to agrochemical use in the U.S. The results show that bird decline are, in fact, most correlated to pesticide use, rather than the intensification of crop production.

A CLAIM that present proposals 
to ban neonicotinoid insecticides and introduce onerous new regulations on other chemicals up for approval could lead to a complete loss of investment by major chemical companies was made yesterday. Mike Bushell is the principal scientific advisor with Syngenta, the Swiss-based chemical company currently embroiled in a battle to retain the use of one of its major pesticides used in the treatment of oilseed rape seed. He was adamant that no-one would invest in any future programme of insecticide approval if new regulations came in. "Any new product with even moderate toxicity to bees would require an incredibly expensive field programme using thousands of beef hives. It would be impossible and impractical to run such a programme and nobody would invest in it,” he said. He believed that much of the current furore over the future use of neonicotinoids was ideologically driven by those who wished to remove all crop protection products from the market.