摘要:

To fight against pests and vectors of certain diseases, Cameroon imports and makes use of pesticides. Importation and utilization are subject to regulation from importers to users. The goal of this study is to evaluate the actual regulatory system of pesticides in Cameroon. From this study has emerged the fact that Cameroon has insufficient legislation for pesticides. Registration does not exist, and the ministry of agriculture restricts itself to issuing attestation of importation, if the product is effective, to those who write an application. Importation and distribution are done in conditions that are far from ideal. To remedy this inadequacy, it is necessary to train and inform all those intervening in this domain and put in place research infrastructures. Appropriate legislation elaborated in a broad consultation with competent authorities in pesticides is also needed.

ISSN:0098-4108    

DOI:10.1080/15287399309531732

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This article is a review of blood cholinesterase activity in a cohort of urban pesticide applicators ranging from 1680 to over 3800 workers. During the period 1981–1991, 208, 788 blood samples were taken for measurement of cholinesterase activity with an average of 6 samples per year from each worker. A total of 150 workers or 0.44% of the cohort was removed from exposure to cholinesterase‐inhibiting insecticides because of decreased cholinsterase activity. No worker required treatment for signs of cholinesterase inhibition.

ISSN:0098-4108    

DOI:10.1080/15287399309531733

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Previous studies from this labortory have shown that 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) decreased complement component C3 levels in female B6C3F1 mouse serum following in vivo acute or subchronic exposure (White et al., 1986). Since TCDD is a hepatotoxic compound and more than 90% of serum C3 is produced by the liver, studies were undertaken using mouse Hepa 1c1c7(Hepa 1) hepatoma cell line to determine if TCDD acts directly on hepatocytes to inhibit C3 production. The C3‐producing capacity of Hepa 1 cells was first examined. When confluent Hepa 1 cell monolayers were cultured in 24‐well plates with serum‐free medium, a detectable amount of C3 (14.1 ± 0.8 ng/ml) was secreted as early as 1 h after culture and reached a plateau at 12 h (68.3 ± 4.9 ng/ml). Furthermore, the sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PACE) analysis demonstrated that the molecular weight of C3 in culture supernatant corresponded to that present in mouse serum. Human recombinant IL‐1β (hrlL‐1β), a known inducer of complement C3, at doses as low as 1 unit/ml increased the C3 production to 158% of control after 24 h of incubation. The effect of hrlL‐1β was dose dependent, and the maximum tested dose of 10 units/ml increased C3 production to 256% of control. When cells were directly exposed to TCDD at concentrations from 10−10to 10−6M, there was no inhibitory effect on production of C3. TCDD also failed to block the stimulatory effect of 10 units/ml hrlL‐1β added to the culture 1 h later. To verify that cultured Hepa 1 cells were able to respond to TCDD, 7‐ethoxyresorufin O‐deethylase (EROD) activity was measured under the same conditions. TCDD dose‐dependently increased EROD activity of Hepa 1 cells at 24 h following exposure. The activity reached 56.7 ± 3.0 pmol/min/mg protein with 10−9M TCDD, compared with 10.7 ± 1.7 pmol/min/mg protein of vehicle‐exposed cells. Our results indicate that the direct interaction of TCDD with Hepa 1 cells does not affect their C3‐producing capacity, although EROD activity, a characteristic response mediated by the cellular TCDD/Ah receptor, was induced. The lack of effect of TCDD in vitro suggests that the decrease of serum C3 levels observed in vivo may result from an indirect effect of TCDD on hepatocytes.

ISSN:0098-4108    

DOI:10.1080/15287399309531734

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Calcium/magnesium salts of L‐glutamate and L‐ascorbate were tested for modification potential using a rat multiorgan carcinogenesis bioassay. Following sequential treatment with three different carcinogens (diethylnitrosamine, N‐methylnitrosourea, and dihydroxydi‐N‐propylnitrosamine) over a 4‐wk period, rats were given diet containing 5% monocalcium di‐L‐glutamate tetrahydrate (Ca‐glutamate), 2.5% monomagnesium di‐L‐glutamate tetrahydrate (Mg‐glutamate), 5% L‐glutamic acid, 5% monocalcium di‐L‐ascorbate dihydrate (Ca‐ascorbate), 2.5% monomagnesium di‐L‐ascorbate dihydrate (Mg‐ascorbate), or 5% L‐ascorbic acid for 16 wk. Body weight increase was slightly suppressed in the groups receiving Ca‐ascorbate, Mg‐ascorbate, and ascorbic acid supplementation after the carcinogen treatments. While administration of Ca‐glutamate or Ca‐ascorbate raised urinary pH, ascorbic acid values were decreased. Concentrations of calcium and magnesium ions in the urine increased after ingestion of Ca‐glutamate or Ca‐ascorbate, and Mg‐glutamate or Mg‐ascorbate, respectively, but phosphorus levels decreased in all groups given calcium and magnesium salts. No consistent treatment‐related changes in the concentrations of sodium or potassium ions in the urine were detected. Histopathological investigation at wk 20 did not demonstrate any modification of tumorigenesis with regard to the incidence of frequency of lesions developing in the various target organs/tissues. The present results thus revealed no apparent enhancement of carcinogenesis at any site, including the urinary system, by calcium or magnesium salts using the present rat multiorgan carcinogenesis bioassay.

ISSN:0098-4108    

DOI:10.1080/15287399309531735

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Dietary supplementation with bisacodyl at concentrations ranging from 1 to 0.3% was found to induce both calculi and epithelial proliferative lesions, including a transitional‐cell carcinoma, in the urinary bladder of F344/DuCrj rats. In order to clarify the relationship between the bisacodyl‐associated urinary bladder calculi and the development of proliferative lesions in the urinary bladder, male and female rats were administered bisacodyl‐diets at concentrations of 0.3, 0.1, and 0.03% for 32 wk. Both sexes of animals treated with bisacodyl suffered from diarrhea throughout the experimental period. Epithelial proliferative lesions and calculus formation were observed only in the urinary bladder of male rats given the 0.3% bisacodyl diet. Proliferative lesions and increases of bromouracil deoxyriboside (BUdR) labeling indices were found only in the urinary bladder epithelium of rats with calculi, the severity of the former correlating with the calculus weight and being most marked in the dome areas, which are susceptible to physical stimulation. These findings indicate a close relationship between the development of proliferative lesions and the existence of calculi in the urinary bladder, and suggest that bisacodyl‐induced proliferative lesions are not caused directly by bisacodyl per se but are secondary to calculus formation.

ISSN:0098-4108    

DOI:10.1080/15287399309531736

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An animal model using rats was developed to initiate investigations on the bioavailability of different sources of environmental lead. Lead must be absorbed and transported to target organs like brain, liver, kidney, and bone, before susceptible cells can be harmed. The bioavailability and therefore the toxicity of lead are dependent upon the route of exposure, dose, chemical structure, solubility, particle size, matrix incorporation, and other physiological and physicochemical factors. In the present study male F344 rats were fed ≤ 38 μm size particles of lead sulfide, lead oxide, lead acetate, and a lead ore concentrate from Skagway, Alaska, mixed into the diet at doses of 0, 10, 30, and 100 ppm as lead for 30 d. No mortality or overt symptoms of lead toxicity were observed during the course of the study. Maximum blood lead concentrations attained in the 100 ppm groups were ∼80 μg/dl in rats fed lead acetate and lead oxide, and were ∼10 μg/dl in those fed lead sulfide and lead ore concentrate. Maximum bone lead levels in rats fed soluble lead oxide and lead acetate were much higher (∼200 μg/g) than those seen in rats fed the less soluble lead sulfide and lead ore (∼10 μg); kidney lead concentrations were also about 10‐fold greater in rats fed the more soluble compared to the less soluble lead compounds. However, strong correlations between dose and tissue lead concentrations were observed in rats fed each of the four different lead compounds. Kidney lesions graded as minimal occurred in 7/10 rats fed 30 ppm and in 10/10 rats fed 100 ppm lead acetate, but not at lower doses or from other lead compounds. Similarly, urinary aminolevulinic acid excretion, a biomarker for lead toxicity, was increased in rats fed 100 ppm lead acetate or lead oxide, but was unaffected at lower doses or by the less soluble lead compounds. Although the histological and biochemical responses to lead toxicity were restricted to the more soluble lead compounds in this study, lead from Skagway lead ore concentrate and lead sulfide was also bioavailable, and accumulated in proportion to dose in vulnerable target organs such as bone and kidney. Longer‐term studies with different mining materials are being conducted to determine if tissue lead continues to increase, and whether the levels attained are toxic. Data from such studies can be used to compare the toxicity and bioavailability of lead from different sources in the environment.

ISSN:0098-4108    

DOI:10.1080/15287399309531737

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Risk perception studies show that people may underestimate significant risks while overestimating others. Further, government agencies may assume the public becomes aware of risks when the agency has issued advisories, when in reality a segment of the population remains unaware of these warnings. This article reports on a survey of people fishing on the catchment basins of Jamaica Bay Wildlife Refuge in New York City. Of the 154 groups interviewed, only 19% believed the waters or fish were contaminated or unsafe, despite state warnings to the contrary. Fishermen made nearly five visits per month, and ate an average of three fish a week, (remaining fish were eaten by their families) and fish were usually fried. Most people believed the fish were safe to eat, or that they could recognize if one was spoiled. Thus, most people were ignoring the health advisories on consuming fish from these waters. We suggest that these fishermen are unaware of health advisories, or ignore them because the fishing situation is familiar, voluntary, pleasurable, and has not resulted in their illness. Since they believe they can determine if the fish are bad from smell and appearance, they have changed their own analysis from the unknown (chronic, delayed risks from toxics) to the known (immediate illness), lowering their perceived risk, but not the actual risk.

ISSN:0098-4108    

DOI:10.1080/15287399309531738

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Earlier studies from this laboratory have shown that the complement system, especially the component C3, in female B6C3F1 mice is suppressed following TCDD exposure in vivo. However, the direct exposure of TCDD in vitro does not affect the C3‐producing capacity of two types of hepatoma cells, as well as mouse primary hepatocytes. To investigate the effect of TCDD on C3 production by the liver following in vivo exposure, liver intracellular C3 levels and pro‐C3, the precursor of the secreted C3, were examined in the present study. The results demonstrated that there was a dose‐dependent increase of liver intracellular C3 levels (from 138% to 175% of control) immediately following TCDD (from 10 to 40 μg/kg) exposure. This increase was rapid (4 h after exposure), but transient (less than 2 h), and was not accompanied by an alteration of serum C3 levels. Studies using sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PACE) analysis showed that the increase in liver intracellular C3 levels resulted from, at least partially, an increase in intracellular pro‐C3. Serum C3 levels did not decrease until d 3 after exposure, when both liver intracellular C3 levels and pro‐C3 in TCDD‐treated mice were not different from those of the control mice. These results indicated that the modulation of liver intracellular C3 by TCDD did not correlate with the suppression of serum C3 levels following exposure.

ISSN:0098-4108    

DOI:10.1080/15287399309531739

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Highly treated reclaimed wastewater was evaluated as a possible supplement to raw water sources required to meet San Diego's growing need for potable water. Biomonitoring experiments employing fathead minnows(Pimephales promelas)were used to compare reclaimed water with the city's current raw water supply. Juvenile fish were exposed in flow‐through aquaria in field laboratories located at the reclamation plant (AQUA II) and at a municipal potable water treatment facility (Miramar). Biomonitoring measurements were survival and growth, swimming performance, and trace amounts of 68 base/neutral/acid extractable organics, 27 pesticides, and 27 inorganic chemicals found in fish tissues after exposure. Biomonitoring revealed differences in survival, growth, and swimming performance only after 90‐ and 180‐d exposure. Reclaimed water and raw water were not readily distinguishable in 28‐d chemical bioaccumulation tests in terms of organic chemical contaminants in fish tissue except for pesticide levels, which tended to be higher in raw water. Similar inorganic species were found in samples from both waters, although there was greater evidence of bioaccumulation of certain contaminants from raw water. Based on biomonitoring parameters included in these experiments, the use of reclaimed water to supplement raw water supplies would appear to pose no major public health threats. The results of these studies will be combined with additional health effects information before final conclusions are reached about the suitability of reclaimed water for human consumption.

ISSN:0098-4108    

DOI:10.1080/15287399309531740

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Prediction of a positive result in rodent carcinogenesis bioassays using two instead of four sex‐species groups is examined for the subset of chemicals in the Carcinogenic Potency Database that have been tested in four sex‐species groups and are positive in at least one (n = 212). Under the conditions of these bioassays, a very high proportion of rodent carcinogens that are identified as positive by tests in four groups is also identified by results from one sex of each species (86–92%). Additionally, chemicals that are classified as “two‐species carcinogens” or “multiple‐site carcinogens” on the basis of results from four sex‐species groups are also identified as two‐species or multiple‐site carcinogens on the basis of two sex‐species groups. Carcinogenic potency (TD50) values for the most potent target site are similar when based on results from two compared to four sex‐species groups. Eighty‐five percent of the potency values are within a factor of 2 of those obtained from tests in 4 sex‐species groups, 94% are within a factor of 4, and 98% are within a factor of 10. This result is expected because carcinogenic potency values are constrained to a narrow range about the maximum dose tested in a bioassay, and the maximum doses administered to rats and mice are highly correlated and similar in dose level.

ISSN:0098-4108    

DOI:10.1080/15287399309531741

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor