Transplacental mutagenesis of products formed in the stomach of golden hamsters given sodium nitrite and morpholine

Nitrate in Drinking Water and Time to Pregnancy or Medically Assisted Reproduction in Women and Men: A Nationwide Cohort Study in the Danish National Birth Cohort

Purpose

No studies have investigated if drinking water nitrate affects human fecundity. Experimental studies point at detrimental effects on fetal development and on female and male reproduction. This cohort study aimed to explore if female and male preconception and long-term exposure to nitrate in drinking water was associated with fecundability measured as time to pregnancy (TTP) or use of medically assisted reproduction (MAR) treatment.

Methods

The study population consisted of pregnant women recruited in their first trimester in 1996–2002 to the Danish National Birth Cohort. Preconception drinking-water nitrate exposure was estimated for the pregnant women (89,109 pregnancies), and long-term drinking water nitrate exposure was estimated from adolescence to conception for the pregnant women (77,474 pregnancies) and their male partners (62,000 pregnancies) by linkage to the national drinking water quality-monitoring database Jupiter. Difference in risk of TTP >12 months or use of MAR treatment between five exposure categories and log-transformed continuous models of preconception and long-term nitrate in drinking water were estimated. Binominal regression models for risk ratios (RR) were adjusted for age, occupation, education, population density, and lifestyle factors.

Results

Nitrate in drinking water (median preconception exposure: 1.9 mg/L; median long-term exposure: 3.3 mg/L) was not associated with TTP >12 months or use of MAR treatment, neither in the categorical nor in the continuous models.

Conclusion

We found no association between preconception or long-term exposure to drinking water nitrate and fecundability.

6 Final Report on the Safety Assessment of Morpholine

Morpholine is used in cosmetic products as a surfactant and emulsifier at concentrations up to 5%.

Morpholine is metabolized in guinea pigs but was not significantly metabolized in rats, dogs, or rabbits. Dermal LD50s in rabbits ranged between 0.3 and 1.2 g/kg. The oral LD50s in rats were between 1.1 and 1.6 g/kg; in guinea pigs the oral LD50 was 0.9 g/kg.

In studies of acute and short-term dermal toxicity Morpholine as an undiluted and unneutralized solution or as a diluted and unneutralized solution applied daily to the skin of guinea pigs and rabbits, respectively, caused the deaths of the test animals within 2 weeks. In both cases, the skin was necrotic.

Unneutralized solutions of Morpholine caused severe corneal necrosis, but upon neutralization Morpholine was not injurious to rabbit eyes.

In short-term inhalation studies (in rats) with varying concentrations of Morpholine, the effects observed included irritation of the mucous membranes and an increased respiratory rate. Chronic inhalation studies of Morpholine in rats and guinea pigs reported changes in the nervous system activity and arterial and peripheral blood pressure. At high concentrations Morpholine produced swelling of the alveolar cells and atrophy of lymphoid elements in the spleen. At lower concentrations a decrease in the size of the lymph nodules in the spleen was noted.

Morpholine was a weak positive mutagen in L5178 mouse lymphoma assay, in BALB/3T3 malignant cell transformation and fibroblast transformation assays, and in sister chromatid exchange assays, but was negative in the Ames test with and without metabolic activation. At nontoxic doses Morpholine did not increase the rate of DNA repair in rat hepatocytes. Results of other mutagenic assays varied according to the system used.

Nitrosation of Morpholine produces N-nitrosomorpholine, which has been mutagenic in a variety of test systems. Simultaneous exposure of laboratory animals to Morpholine and nitrites has caused a number of different cancers. A carcinogenic response was produced in rats in a long-term feeding study of Morpholine in which nitrites were present in the diet.

In humans, Morpholine is absorbed and is considered to be a skin and eye irritant, as well as a skin sensitizer. A formulation containing 1% Morpholine indicated that the ingredient was neither an irritant nor sensitizer.

Morpholine is not considered to be an animal carcinogen. It reacts easily with nitrosating agents, resulting in the formation of N-nitrosomorpholine. Under conditions of use, it is highly unlikely that Morpholine is totally free of carcinogenic nitrosoamines. Without quantitative data regarding the formation of N-nitrosomorpholine under conditions of use, it cannot be concluded that Morpholine is safe for use in cosmetic products.

Chronic toxicity of sodium nitrite in the male F344 rat

A long-term feeding study was carried out in rats with sodium nitrite. The test substance was administered as part of a reduced-protein diet to groups of 50, 6-wk-old, male F344 rats at dose levels of 0.2 or 0.5% (w/w) sodium nitrite for up to 115 wk. A control group of 20 males received the reduced-protein diet alone. Throughout the study, there was a dose-related decrease in the rates of body-weight gains and a corresponding decrease in body weights among animals fed sodium nitrite in the diet. Food intakes of rats in the low-dose group were slightly raised over most of the study. In the high-dose group, food intakes were reduced during the first month, but thereafter were similar to those of the control group. This reduction in food intake together with the lower body weights in the nitrite-treated animals, may indicate a reduction in food utilization. In the first week of treatment the following haematological parameters were reduced: red blood cell count, haematocrit and haemoglobin concentration. The red blood cell count continued to fall for 8 wk, then slowly returned to normal by wk 52. A dose-related reduction was noted in both the incidence and time of onset of lymphomas, leukaemias and testicular interstitial cell tumours. Leukaemias were only found in animals with lymphoma, indicating an association between the two lesions. Under the conditions described in this study, sodium nitrite was found not to be carcinogenic when fed to rats in the diet for up to 115 wk, but rather that the incidence of tumours was reduced in a dose-related manner, which correlated with a similar trend in body weights.

Micronucleus tests in mice on 39 food additives and eight miscellaneous chemicals

A total of 47 chemical substances including 32 synthetic food additives, seven additives from natural sources, three trihalogenated methanes, two fluoro-compounds for dental use, one insecticide, and two other compounds were subjected to the micronucleus test in mice. Five compounds, i.e. chlorine dioxide, maltol, potassium bromate, sodium chlorite and sodium dehydroacetate, were found to induce micronuclei after a single ip injection. Potassium bromate, sodium chlorite and sodium dehydroacetate were tested further by oral administration, and potassium bromate showed a clearly positive result. Almost all the compounds which were negative with the single treatment were additionally tested by four or five multiple treatments, but none showed any indication of micronucleus induction.

Evaluation of the nitrate drinking water standard with reference to infant methemoglobinemia and potential reproductive toxicity

In view of published results of epidemiologic studies which suggested an association between nitrate in drinking water and human malformations, an assessment of the toxicology of nitrates and nitrites in relation to possible adverse effects on reproduction and development was performed. The current water standard for nitrate is based on protection from methemoglobinemia. A review of the animal data failed to provide evidence for teratogenic effects attributable to nitrate or nitrite ingestion. Adverse reproductive effects reported occurred at doses that were about one thousand times and higher than the estimated human intake. Neither nitrate nor nitrite in experimental animals concentrated in the mammary gland or milk. The present assessment concludes that the maximum contaminant level of 45 ppm nitrate ion, or 10 ppm nitrate-nitrogen, adequately protects the very young from nitrate-induced toxicity, both pre- and postnatally.

Aneuploidy in mammalian somatic cells in vivo

Aneuploidy is an important potential source of human disease and of reproductive failure. Nevertheless, the ability of chemical agents to induce aneuploidy has been investigated only sporadically in intact (whole-animal) mammalian systems. A search of the available literature from the EMCT Aneuploidy File (for years 1970-1983) provided 112 papers that dealt with aneuploidy in mammalian somatic cells in vivo. 59 of these papers did not meet minimal criteria for analysis and were rejected from subsequent review. Of the remaining 53 papers that dealt with aneuploidy induction by chemical agents in mammalian somatic cells in vivo, only 3 (6%) contained data that were considered to be supported conclusively by adequate study designs, execution, and reporting. These 3 papers dealt with 2 chemicals, one of which, mercury, was negative for aneuploidy induction in humans, and the other, pyrimethamine, was positive in an experimental rodent study. The majority of papers (94%) were considered inconclusive for a variety of reasons. The most common reasons for calling a study inconclusive were (a) combining data on hyperploidy with those on hypoploidy and/or polyploidy, (b) an inadequate or unspecified number of animals and/or cells per animal scored per treatment group, and (c) poor data presentation such that animal-to-animal variability could not be assessed. Suggestions for protocol development are made, and the future directions of research into aneuploidy induction are discussed.