William L. Downs

Oral toxicity and metabolism of diuron (N-(3,4-dichlorophenyl)-N′,N′-dimethylurea) in rats and dogs

Abstract Diuron ( N -(3,4-dichlorophenyl)- N′,N′ -dimethylurea) has a relatively low order of acute oral toxicity in the rat. The LD 50 (14-day) for males was 3·4 g/kg. Ten daily doses of 1 g/kg were not lethal but growth depression was observed. In both studies, increased erythropoiesis was indicated histologically. Skin irritation and sensitization tests in guinea-pigs proved negative. 90-Day feeding studies in rats disclosed no growth depression at a dietary level of 400 ppm or less; slight in males at 2000 ppm; marked in both sexes at 2500 ppm and higher. Slight anaemia and enhanced erythropoiesis were observed at 250 ppm in females and in both sexes at 2500 ppm and above. An abnormal blood pigment, identified as sulphaemoglobin was detected at 2000 ppm and higher. Feeding studies on two dogs revealed no effect at 160 ppm for 1 month but slight growth retardation and a moderate anaemia were induced by 2-month feeding of increasing dietary levels commencing at 400 ppm and terminating at 2400 ppm. 2-Yr feeding studies were conducted on rats and dogs at dietary levels of 0, 25, 125, 250 and 2500 ppm. No effect was seen at the 25, 125 or 250 ppm levels in either species with the exception of a trace of abnormal blood pigment in some animals on 125 or 250 ppm diuron and of a trend towards reduced erythrocyte counts in dogs on 250 ppm. At the highest level of 2500 ppm the principal findings in both species were growth retardation, slight anaemia, presence of abnormal blood pigment, enlargement of spleen (occasionally in rats) and of liver (dogs) and increased erythropoiesis with splenic haemosiderosis. No histological changes were seen at any level and there was no evidence of carcinogenicity. In a three-generation reproduction study in rats maintained on 0 or 125 ppm diuron, no untoward findings were obtained. In metabolic studies in rats and dogs fed 25–2500 ppm diuron for 9 months–2 yr, tissue residue levels were proportional to the dietary intake of diuron but no tissue storage occurred. Excretion occurred in both faeces and urine. N -(3,4-Dichlorophenyl)urea was the predominant metabolite in the urine; small amounts of N -(3,4-dichlorophenyl)- N′ -methylurea, 3-4-dichloraniline, 3,4-dichlorophenol and unchanged diuron were also detected.

Tests on mice for evaluating carcinogenicity

Six chemical compounds were tested for carcinogenic potency in mice (C3H/Anf) by subcutaneous implantation or repeated skin application. Three compounds, aminotriazole, Aramite [2-(p-tert-butylphenoxy)isopropyl 2-chloroethyl sulfite], and Flectol H (a polymer of 1,2-dihydro-2,2,4-trimethylquinoline), were carcinogens or suspected carcinogens. Three compounds, butylated hydroxyanisole, dioctyl adipate, and methoxychlor had shown no carcinogenic potential when fed chronically to rats and dogs. Six groups of 100 mice (50 of each sex) were given single, subcutaneous injections (10 mg/mouse) of the test compounds. A seventh group of 100 mice was given the injection vehicle only (trioctanoin) and served as controls. No evidence of carcinogenic activity attributable to the treatment was noted over periods of observation averaging 273–575 days. Six groups of 100 mice (50 of each sex) were given weekly skin applications of 0.1 mg of the test compound in acetone, and six additional groups of 100 mice were given weekly applications of 10 mg of the test compound in acetone. A total of 200 control mice (100 of each sex) were given weekly applications of acetone only (0.20 ml). No gross evidence of tumor formation was detected in the skin of these mice (mean survival times ranged from 310 to 519 days for the low dose and from 309 to 459 days for the high dose). Microscopic examination of the skin from 205 mice from the low-dose study and of 189 mice from the high-dose study showed no evidence of tumors. Test procedures on mice observed for the remainder of their lives and involving weekly applications to the skin or single subcutaneous implantations of chemical agents having low carcinogenic potential are not adequate substitutes for tests by other routes of administration. For the compounds selected, these procedures failed to contribute significant additional information.

Toxic effects of fluoride on the rat kidney. II. Chronic effects.

Abstract 1. 1. The 30-day LC50 of sodium fluoride administered in the drinking water was 205 ppm fluoride in the weanling rat. Death generally occurred between the third and fifth day after administration was begun. When levels of 150–250 ppm fluoride were administered in the water, 30–40% of the surviving rats showed a renal lesion consisting of dilatation of the tubules at the corticomedullary junction. 2. 2. Levels of 0, 1, 5, 10, 25, 50, and 100 ppm fluoride were administered in the drinking water to rats for 6 months. No growth depression was seen, even at 100 ppm, but mortality was slightly increased in males and females ingesting 50 ppm and males ingesting 100 ppm. The only pathologic changes were seen in the kidney and the bone. Two of the 12 rats receiving 100 ppm for 6 months showed a marked dilatation of the tubules in the corticomedullary region of the kidneys. The lesion was accompanied by a high water consumption and urine output. Radiographically, an increase in the deposition of trabecular bone was seen in the rats ingesting 100 ppm fluoride. A slight increase was also seen in the males ingesting 50 ppm fluoride. 3. 3. Balance studies showed that rats retained about 50% of the ingested fluoride after 3 months on fluoridated water. Seventy-five to 80% of the ingested fluoride was absorbed, and 65–70% of the absorbed fluoride was retained. After 6 months, the male rats retained 45% of the ingested fluoride, the females about 60%. Both males and females absorbed 80% of the ingested fluoride. The males retained 60% of the absorbed fluoride; the females, 80%. The percentage fluoride retained was independent of the fluoride level in the water. The increased age of the rats did not alter fluoride retention, except that the females retained a higher percentage of the ingested fluoride than the males after 6 months. 4. 4. The fluoride concentration in the femur ash of the rats ingesting fluoridated water for 3 months was directly proportional to the fluoride level in the water, even with a level of 100 ppm. After 6 months, the fluoride concentration was directly proportional to the fluoride level in the water at levels of 50 ppm and less. The rats ingesting 100 ppm fluoride in the water had a lower concentration than would be expected from this proportionality. 5. 5. The natural fluoride present in a stock animal ration such as Purina Fox Chow Meal was of limited availability. Only 10–15% of this fluoride was metabolized by the rat.

Toxicity of sodium cyanurate

Abstract Sodium cyanurate fed to rats for 20 weeks and to dogs for 6 months was without evident adverse effects at a dietary concentration of 0.8%. Rats fed 8% of sodium cyanurate in the diet for 20 weeks showed consistent and characteristic histologic changes in the kidneys, consisting of dilatation of the distal collecting tubules and ducts of Bellini with focal areas of epithelial proliferation. Similar renal changes were observed in dogs fed 8% of sodium cyanurate in the diet for 16–24 months. Five milliliters of an 0.8% or 8% aqueous suspension of sodium cyanurate applied daily, 5 days/week, to the skin of rabbits for 3 months caused no adverse effects at the lower concentration. At the higher concentration, kidney changes similar to, but less marked than, those described in the rats and dogs were noted. No skin irritation was caused by either concentration. No eye irritation was observed in rabbits receiving 0.1 ml daily, 5 days/week, of an 8% aqueous suspension of sodium cyanurate instilled into one eye over a period of 3 months.

CHRONIC FEEDING STUDIES OF BUTYLATED HYDROXYANISOLE IN DOGS.

Groups of three dogs each were maintained for one year on diets containing the following amounts of BHA as a 50% solution in propylene glycol: 0 (control group), 0.3, 3.0, 30, and 100 mg/kg. An additional group received a 30 mg BHA/kg as a 20% solution in propylene glycol containing about 6% propylgallate and 4% citric acid. Body weights increased slightly or were maintained in every dog except one. The dogs were in good condition during the year; there were no deaths. Urine analyses initially and at the end showed normal values for sugar and protein. Blood samples taken on nine occasions during the study gave normal hematologic values. Organ weights lay in the normal ranges. There was no storage of BHA in fat, brain, liver, and kidney; and there was no increase in urinary reducing substances. Thorough histologic examinations revealed no evidence of any tissue change that was attributed to the administration of BHA.

Oral toxicity of linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea) in rats and dogs

Abstract The Approximate Lethal Dose of linuron administered orally to rats ranged from 1·0 to 2·25 g/kg and that of a wettable powder formulation containing 50% linuron was 7·5 g/kg. Ten daily oral doses of 0·2 g linuron/kg depressed weight gain but did not affect histology. Short-term rat studies established a no-effect level of 60–80 ppm in the diet, with growth depression at higher levels and (at 1200–3000 ppm) an abnormal blood pigment. A dietary level of 125 ppm fed to rats for 2 yr had no adverse effect, but 625 ppm caused growth depression, possible anaemia and increased erythrogenesis. In two reproduction studies in rats, feeding of 125 ppm linuron had no effect on reproductive performance or post-weaning growth. Feeding of 120 ppm to dogs for 1 month had no effect, but 1200 ppm caused slight anaemia and weight depression. Traces of abnormal blood pigment were found in female dogs given 25 ppm linuron in the diet for 2 yr, and at the 625 ppm level there was anaemia, increased erythrogenesis and abnormal blood pigment in both sexes. No evidence of carcinogenicity was provided by these studies. Feeding of 25 or 125 ppm linuron to rabbits during days 8–16 of pregnancy provided no evidence of any embryotoxic or teratogenic effects.

The approximate oral toxicity in rats of selected household products

Abstract The acute, “screening,” oral toxicities of about 40 common household products purchased in neighborhood stores were determined in adult albino female rats. All products fell in toxicity classes 1, 2, or 3 as defined in Gleason et al. (1957), i.e., had lethal doses greater than 500 mg/kg. From the standpoint of acute oral toxicity, appropriate labeling is suggested for substances lethal in amounts of 500 mg/kg or less unless experience has demonstrated a negligible hazard; substances of lesser toxicity would remain unlabeled unless hazard was demonstrated.

Toxicological and radioprotection studies on S,beta-aminoethylisothiuronium bromide (AET).

AET was moderately toxic when administered in single doses to mice, rats, rabbits, guinea pigs, and cats. When given by intravenous injection, doses ranging from 50 to 450 mg/kg were lethal; by intraperitoneal injection, the lethal range was 350 to 650 mg./kg. Administered orally as a single dose, the lethal range was 250 to 1000 mg/kg. Rats fed dietary levels of 0.1%, 0.3%, and 0.5% for a period of 1 month showed no effects on growth. A 1.0% dietary level produced a moderate depression of growth. An increase in white cell counts was observed at all dietary levels of AET. No histological lesions were found that could be attributed to the ingestion of AET. The protective effects of S, BETA aminoethylisothiuronium - Br - HBr - (AET) against the lethal effects of 594 r of 1-Mev x radiation was tested in 21 dogs, with 14 additional dogs as controls. Data presented indicate failure of this compound to enhance survival or survival rate. (auth)

Screening of fluorine-containing compounds for acute toxicity

Abstract The maximal tolerated dose and the minimal lethal dose in mice are estimated for a series of twenty flucrine-containing organic compounds, four inorganic compounds of fluorine, and three nonfluorine-containing organic compounds.

Renal effects of potassium niobate

Abstract The renal effects of a single intravenous dose of 30 mg/kg of niobium as potassium niobate were observed in female mongrel dogs and in female albino rats for various time intervals up to 30 days. In dogs, niobium produced marked decreases in glomerular filtration rate, the maximal rate of tubular secretion of p -aminohippurate, and the maximal rate of tubular reabsorption of glucose. Histologic studies of the kidneys revealed injuries in both the proximal and the distal tubules. Some tubular lumina were filled with granular pigment throughout all levels of cortex and medulla, while others contained casts. The epithelial cells were flattened in some areas and necrotic in others. Niobium-poisoned rats showed marked increases in water intake and urine volume, and decreases in urinary density and osmolality. Urinary sodium execretion increased for the first 2 days but decreased on day 7. Rats lost their urine-concentrating ability, failed to respond to injection of antidiuretic hormone, and peak urine excretion rate after a water load was delayed. Increases in kidney weight and kidney weight to body weight ratios were noted. The renal histologic changes, like those in dogs, involved both proximal and distal tubules, and consisted of tubular dilation and the presence of scattered hyaline casts and deposits of granular pigment. Tubules occasionally showed necrosis, regeneration, and early fibrosis.