Pesticide residues in the total diet in England and Wales, 1966–1967: III.—Organophosphorus pesticide residues in the total diet

Details are given of the methods of analysis used in the determination of Organophosphorus pesticide residues in each of the food groups into which the total diet samples were divided. Residues of only 6 pesticides were detected. Malathion was the most commonly found, mainly in the cereal foods group of the diet, but all the residues were at low levels.     

Pesticide and other chemical residues in total diet samples (XI)

In the Total Diet study, the Food and Drug Administration has, since 1964, reported residues of pesticides and other chemicals ingested in the average diet of the Nation's largest eater, the young adult male. During the eleventh year of the study, pesticide residues remained at the relatively low levels reported previously. Twenty market baskets were collected in 20 cities which ranged in population from less than 50,000 to 1,000,000 or more. Averages and ranges of residues found are reported for August 1974 through July 1975 by food class. The individual items used in making up the dairy and meat composites in four market baskets were analyzed for pesticides and the results are included. Data for lead, cadmium, selenium, mercury, arsenic, and zinc are also included. Results of recovery studies within various classes of residues are also presented.     

Pesticide residues in the total diet in Canada. III—1971

Foods, representing an average Canadian diet, were cooked, grouped by type of product and made into composites which were then analysed for organochlorine and organophosphorus pesticides and arsenic. The amounts found were at a consistently low level and would contribute approx. 22 μg total pesticide residues and 25 μg arsenic/person/day.     

Pesticide residues in the total diet in Canada II—1970

Composites of food representing the Canadian diet were analysed for organochlorine and organophosphorus pesticides and arsenic. Thirteen organochlorine and three organophosphorus pesticides were found. Residues were consistently low and would contribute to the diet approximately 20 μg total pesticide residues and 30 μg arsenic per person per day.     

Pesticide residues in foodstuffs in Great Britain XIV.—Mercury residues in potatoes

The total mercury contents of the skin and flesh fractions of potatoes from 87 commercial crops grown in England were in the range 0.0–0.08 ppm with the majority in the range 0.01–0.04 ppm.     

Pesticide residues in the total diet in Canada

A total diet, representative of a Canadian's daily food intake was formulated, grouped by types of food, and prepared as for eating. Analysis of these composites for residues showed eleven organochlorine but no organophosphorus pesticides. Residues were low and would yield an average total daily intake of 24μg/person/day. The level of arsenic was determined on one-quarter of the samples and was found to be consistently below 0.1 ppm.     

Pesticide residues in total diet samples (VIII).

During the eighth year of the Total Diet Study, residues remained at the relatively low levels reported previously. A total of 35 market baskets were collected in 32 cities which ranged in population from less than 50,000 to 1,000,000 or more. Averages and ranges of residues found are reported for the period June 1971 through July 1972 by region and food class. Results of recovery studies within various classes of residues are also presented.     

Pesticide residues in the total diet in Canada. IV. 1972 and 1973

Foods, representing an average Canadian diet, were prepared for eating, made into homogenised composites, each containing one type of produce, and analysed for pesticide residues and arsenic. The amounts found were at a consistently low level which could contribute approximately 20 μg total pesticide residues and 35 μg arsenic/person/day.     

Activity of the botanical aphicides 1,5‐diphenyl‐1‐pentanone and 1,5‐diphenyl‐2‐penten‐1‐one on two species of Aphididnae

1,5‐Diphenyl‐1‐pentanone (A) and 1,5‐diphenyl‐2‐penten‐1‐one (B) are natural products extracted for the first time from Stellera chamaejasme. Laboratory bioassay showed that the two products have strong contact activity and very good anti‐feedant activity against Aphis gossypii and Schizaphis graminum. Both products showed dose‐dependent relationships for both forms of activity against the two aphids, the contact activity of B being about twice that of A. Both products were inferior to methomyl in contact activity but superior in anti‐feedant activity against the two aphids. This is the first report of aphicidal activity in these two compounds, which may represent a new class of aphicide. © 2001 Society of Chemical Industry     

Concentrations of total mercury in several fishes from Delaware Bay, 1975

Mercury levels in eleven species of fishes collected from lower Delaware Bay in April 1975 ranged from 0.018 to 0.321 microgram/g and averaged 0.092 microgram/g. Raja eglanteria, the clearnose skate, had the highest mean mercury concentration (0.214 microgram/g). No correlation was found with feeding habits. These assays provide baseline data for future measurement of mercury accumulation by fishes in this region.     

Competition between Solanum nigrum and pepper in the presence of Meloidogyne incognita

The influence of the root-knot nematode Meloidogyne incognita (Kofoid & White) Chitwood on the competitive relationships between pepper (Capsicum annuum L.) and Solanum nigrum L. (black nightshade) was investigated in a glasshouse experiment. Seven competition treatments were set up: two intraspecific for the crop and the weed and five interspecific treatments in which the emergence of S. nigrum plants was progressively delayed with respect to that of the pepper. Nematodes reproduced in every inoculated plant and their multiplication rates were high in both pepper and S. nigrum. The parasite reduced all growth and yield parameters of the crop, but did less harm to the weed. The negative effect of S. nigrum on pepper peaked in the treatment in which the weed and pepper plants emerged together. S. nigrum was a stronger competitor than pepper under both nematode-infested and nematode-free conditions. The effect of nematodes on pepper yield was less than that of competition, but both appeared to be additive.     

The effect of some heavy metal ions on photosynthesis in a freshwater alga

The effect of the following metals: copper, cadmium, lead, mercury, methyl mercury, and thallium, and the herbicide 3(3,4-dichlorophenyl)1,1-dimethylurea on (a) the light-induced oxygen evolution, (b) the Hill reaction (water → dichlorophenol-indophenol), and (c) a modified Mehler reaction (dichlorophenol-indophenol → methyl viologen) was studied with the freshwater alga Chlamydomonas reinhardii.The light-induced oxygen evolution of whole cells was found to be very sensitive to the cadmium ion, but this ion was almost without effect on the Hill reaction and the modified Mehler reaction. The light-induced oxygen evolution was also very sensitive to methyl mercury and lead.     

Mercury concentrations in fish, North Atlantic offshore waters--1971.

Mercury concentrations were determined in muscle and liver of 41 species of fish and a limited number of plankton, sediment, and invertebrate samples collected from North Atlantic offshore waters in 1971. The average mercury concentration in fish muscle was 0.154 ppm with a standard deviation of 0.124. Invertebrate samples had mercury concentrations which were generally less than 0.1 ppm. In a single lobster sample, however, 0.31 ppm mercury was found in the tail muscle and there was 0.60 ppm in the liver. Mercury levels in all 9 plankton and 10 sediment samples taken were less than 0.05 ppm.     

Moisture content and dormancy in Striga asiatica seeds

Freshly harvested Striga asiatica L. seeds will germinate in response to a stimulant only after the passage of time, an after-ripening period, and exposure to moisture at a suitable temperature, a conditioning period. To investigate the role of seed moisture content in the regulation of the after-ripening period, seeds were placed in chambers having specific relative humidity of 6%, 14%, 33%, 75% and 91% for 30, 60, 90 and 150 days. The seeds were then conditioned and germination percentage, response to tetrazolium and seed moisture contents were measured. Seeds at moisture contents less than 10% at the start of conditioning had germination of greater than 93%. Seeds at moisture contents over 10% at the start of conditioning could germinate between 60% and 3%, with germination decreasing as seed moisture content at the start of conditioning increased. The highest moisture content (17%) and lowest germination percentage (3%) occurred in seeds stored at 91% relative humidity for 150 days. There was a linear relationship of a high degree of correlation (0.997) between a positive tetrazolium test and germination capacity. Germination capacity of seeds could be changed from 90% to 3% by prolonged storage in water (dilute benomyl solution), causing `wet dormancy', then returned to 90% germination by returning to dry storage. Seed moisture content at the beginning of conditioning appears to control the responsiveness of the seeds to germination stimulants. The implications of these findings to the control of the parasite are discussed.     

Resistance against uprooting in carrots ( Daucus carota) and annual weeds: a basis for selective mechanical weed control

Trials were carried out in order to investigate ways in which to achieve selectivity in mechanical weed control. The influence of soil type, uprooting angle and development stage on the uprooting force of some annual weeds and carrot was studied. Spergula arvensis L., Urtica urens L., Chenopodium album L. and carrot (Daucus carota L.) were sown in soil bins filled with four different soil types. The plants were uprooted when they had two true leaves. Soil type significantly influenced the uprooting force needed by all four species. The forces required to uproot U. urens and C. album differed significantly between peat and loamy sand. In loamy sand, Capsella bursa-pastoris (L.) Med., Stellaria media (L.) Vill, Chamomilla suaveolens (L.) Pursh Buch. and Viola arvensis Murr. could all be uprooted by less force than it took to uproot carrot. The uprooting angle (0°, 45° and 90°) had no significant influence on the uprooting force for carrot at the studied developmental stage. C. album, S. arvensis, U. urens, Matricaria inodora, Thlaspi arvense L. and carrot could all be uprooted by less than 1 N when they had two true leaves. Carrots required a greater uprooting force than the weeds at the three early developmental stages studied. This indicates that it should be possible to develop selective mechanical weed control methods.     

Towards the primary target of chloroacetamides –new findings pave the way

This review reports on research of the last ten years to find the primary target enzyme for chloroacetamides. As could be shown first with the green alga Scenedesmus, the formation of very‐long‐chain fatty acids (VLCFAs) is severely impaired. Subsequently, in short‐term experiments, labelled malonate or stearate could be incorporated into leaf discs of cucumber, barley or leek seedlings. While the formation of ‘normal’ long‐chain fatty acids (up to C18) was not influenced, phytotoxic chloroacetamides strongly inhibited the synthesis of VLCFAs of C20, 22 and 24, with I₅₀ values of 10–100 nM . Inhibition depends on the amide structure and on stereospecificity. Also cafenstrole or recently developed tetrazolinones and phosphosulfonates were found active to inhibit fatty‐acid elongation. Subsequently, a cell‐free elongase assay was developed using a microsomal preparation from leek seedlings (Allium porrum L), [¹⁴C]malonyl‐CoA and C18, 20, or C22 acyl‐CoA primer substrates. All elongation steps were strongly affected by those phytotoxic herbicides which were also active in vivo. The inhibitors form a tight‐binding complex with the condensing elongase enzyme system which develops with time and lowers the I₅₀ values markedly. Apparently, a nucleophilic attack of the inhibitor takes place at the specific target enzyme. Acyl‐CoA elongation inhibition is correlated with growth inhibition of the intact cell. Due to the low I₅₀ values and the specific inhibition, we assume that impaired VLCFA‐formation is the primary phytotoxic impact of chloroacetamides and functionally related structures. © 2000 Society of Chemical Industry     

Mercury(II) ion-promoted hydrolysis of some organophosphorus pesticides

The promotion of hydrolysis of some organophosphorus pesticides by mercury(II) ion was studied. The presence of mercuric chloride at 20 mg litre^?1 increased the initial hydrolysis rates of malathion, fenitrothion, fenthion and parathion-methyl in pH 5.5 buffer by two to three orders of magnitude. The hydrolysis was found to be first order with respect to both mercury(II) ion and the pesticide. The main hydrolysis product was 3-methyl-4-nitrophenol for fenitrothion, and 4-nitrophenol for parathion-methyl. It is postulated that the reaction involves the formation of a 1:1 complex and a very slow regeneration of the mercury(II) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pesticide dichlorvos.