Pesticides in the cultivation of carnations in greenhouses: Part I--Exposure and concomitant health risk.

Respiratory exposure and dermal exposure of the hands and forearms to the pesticides chlorothalonil, thiophanate-methyl, thiram, and zineb during application and during crop activities have been measured on 18 farms for carnation culture in glass-covered greenhouses in the Netherlands. Farms were selected according to a "worst case" strategy with regard to dermal exposure during cutting of flowers. For 94 workers, the geometric mean dermal exposure rate during cutting (measured on long-sleeved cotton glove monitors) was 10.1 mg/hr (active ingredient per unit of actual working time) and during sorting/bundling of these flowers by 35 workers the dermal exposure rate was 7.3 mg/hr. The average concentration in air as measured by personal air sampling during cutting after a pesticide had been dusted was 0.07 mg/m3. For the same area, spraying a pesticide exposed the applicator to a dermal exposure seven times higher than dusting. However, during dusting respiratory exposure was higher. Generally, overall exposure is higher during re-entry activities than during application. From the observed levels of dermal exposure during harvesting (re-entry) and from toxicity data, health risk occurs after application of pesticides that are relatively toxic and show relatively good skin-penetrating properties at relatively high application rates. The respiratory exposure to dusted pesticides after re-entry is about as high as during application of these pesticides and may in some situations also result in health risks. Training and education of greenhouse workers on (personal) hygiene and use of protective gloves are advocated in order to reduce exposure.

Harmonization of criteria documents for standard setting in occupational health: a report of a workshop.

The paper presents the most important points of the discussion, recommendations, and conclusions of a workshop on harmonization of criteria documents (CDs) for standard setting in occupational health, with emphasis on standard setting in the European Community (EC). The objectives were to achieve harmonized CDs and to develop a mechanism for international cooperation. The discussion focused on three broad topics: contents of CDs; collection, assessment, and evaluation of data; and procedures for the preparation and exchange of CDs on specific chemicals. Annex A on the various procedures for standard setting by EC Member States, countries outside the EC, and international organizations and Annex B on the proposed contents of the CDs are also included.

Loperamide: evidence for a centrally mediated opioid effect on rumen motility in conscious goats and sheep.

Loperamide inhibited the frequency and amplitude of cyclical contractions of the rumen in conscious goats (100 micrograms/kg, i.v. and sheep (250 micrograms/kg, i.v.). In goats, the inhibitory effect of loperamide could be prevented by pretreatment with the opiate antagonist naltrexone (greater than or equal to 12.5 micrograms/kg, i.v.) but not by pretreatment with the dopaminergic antagonist domperidone (500 micrograms/kg, i.v.). Intracerebroventricular administration of 1 microgram/kg loperamide in goats significantly depressed ruminal contraction frequency, whereas intravenous administration of 10 micrograms/kg loperamide did not affect cyclical motility. Administered via the carotid artery, loperamide (4 micrograms/kg) depressed both frequency and amplitude of cyclical contractions of reticulum and rumen, whereas the same dose was ineffective via the coeliac artery. In vitro, loperamide (10 nM-100 microM) had no influence on spontaneous activity or tone of the reticular longitudinal muscle strips. It is concluded that loperamide inhibits cyclical ruminal contractions through a central opioid pathway.

Central and local actions of opioids upon reticulo-ruminal motility in sheep.

The effects of opioids and naloxone on cyclical forestomach motility were determined in anaesthetized and conscious sheep. To assess central or peripheral opioid actions, differential routes of administration were used. Possible dynamic effects along the innervating vagovagal reflex arc were investigated electrophysiologically at the cervical level of the vagus nerve. Further, direct influences on the smooth muscle were evaluated in vitro on isolated longitudinal reticular strips. Additionally, the effects of some spasmogenic agents were studied for comparative purposes. In anaesthetized sheep, opioids depressed in an identical manner both the amplitude of spontaneous cyclical contractions and contractions evoked by electrical stimulation of the distal end of the cut cervical vagus. In conscious sheep, low doses of normorphine and loperamide inhibited frequency and amplitude centrally (20 micrograms/kg and 4 micrograms/kg via carotid artery respectively), whereas locally higher dose levels (200 micrograms/kg and 10 micrograms/kg via coeliac artery respectively) affected only the amplitude of cyclical contractions. Furthermore the opioid peptides Leu-, Met-enkephalin and [D-Ala2-Met5]-enkephalinamide preferentially depressed the amplitude of cyclical motility most efficiently if administrated via the coeliac artery. These results indicate the presence both of a central opioid action depressing frequency and amplitude and of a local opioid action depressing only the amplitude of cyclical reticulo-ruminal motility. Opioids did not alter the resting discharge of afferent tension units and similarly failed to modulate tone of reticular strips in vitro, suggesting that the opioids act locally on the intramural neuronal plexus, possibly by diminishing the output of excitatory transmitter. Whether substance P could play a role as a vagal excitatory transmitter besides the classically implicated acetylcholine has been discussed. The central opioid mechanism is probably not situated within the gastric centres but elsewhere in the brain. Naloxone (greater than or equal to 100 micrograms/kg, jugular vein) stimulated the frequency of cyclical ruminal motility only in well-defined experimental conditions, probably via a central mechanism.

Modification by domperidone of dopamine- and apomorphine-induced inhibition of extrinsic ruminal contractions in goats.

Goat ruminal strips reacted with an increase in smooth muscle tone after exposure to apomorphine. This rise in tone could be blocked by domperidone, but not by naltrexone. In vivo, both dopamine and apomorphine caused inhibition of extrinsic ruminal contractions. These effects completely prevented by domperidone pretreatment, whereas naltrexone was not an effective antagonist. These results suggest that apomorphine-induced inhibition of rumen motility is due to DA-receptor activation. The extract location of these DA-receptors remains to be determined.

Opiate antagonists stimulate ruminal motility of conscious goats.

The effect of opiate antagonists was determined on the extrinsic ruminal contractions of conscious goats. These contractions normally occur approximately once per minute. Naltrexone (greater than or equal to mg/kg, i.v.) and naloxone caused a significant increase in the frequency of ruminal contractions; morphine (0.8 mg/kg) depressed both frequency and amplitude. Naltrexone (12.5 micrograms/kg) prevented the response to morphine. These results suggest that an inhibitory opioid system is involved in the control of forestomach motility in goats.