Translational research into species differences of endocrine toxicity via steroidogenesis inhibition by SMP-028--for human safety in clinical study.

SMP-028 is a drug candidate developed for the treatment of asthma. In a 13-week repeated dose toxicity study of SMP-028 in rats and monkeys, differences of endocrine toxicological events between rats and monkeys were observed. In rats, these toxicological events mainly consisted of pathological changes in the adrenal, testis, ovary, and the other endocrine-related organs. On the other hand, in monkeys, no toxicological events were observed. The goal of this study is to try to understand the reason why only rats, but not monkeys, showed toxicological events following treatment with SMP-028 and to eventually predict the possible toxicological effect of this compound on human endocrine organs. Our results show that SMP-028 inhibits neutral cholesterol esterase more strongly than other steroidogenic enzymes in rats. Although SMP-028 also inhibits monkeys and human neutral cholesterol esterase, this inhibition is much weaker than that of rat neutral cholesterol esterase. These results indicate (1) that the difference in endocrine toxicological events between rats and monkeys is mainly due to inhibition of steroidogenesis by SMP-028 in rats, not in monkeys, and (2) that SMP-028 may not affect steroidogenesis in humans and therefore might cause no endocrine toxicological events in clinical studies.

Toxicity of the herbicides diuron, propazine, tebuthiuron, and haloxyfop to the diatom Chaetoceros muelleri.

Conventional photosystem II (PSII) herbicides applied in agriculture can pose significant environmental risks to aquatic environments. In response to the frequent detection of these herbicides in the Great Barrier Reef (GBR) catchment area, transitions towards 'alternative' herbicides are now widely supported. However, water quality guideline values (WQGVs) for alternative herbicides are lacking and their potential ecological impacts on tropical marine species are generally unknown. To improve our understanding of the risks posed by some of these alternative herbicides on marine species under tropical conditions, we tested the effects of four herbicides on the widely distributed diatom Chaetoceros muelleri. The PSII herbicides diuron, propazine, and tebuthiuron induced substantial reductions in both 24 h effective quantum yields (ΔF/Fm') and 3-day specific growth rates (SGR). The effect concentrations, which reduced ΔF/Fm' by 50% (EC50), ranged from 4.25 µg L-1 diuron to 48.6 µg L-1 propazine, while the EC50s for SGR were on average threefold higher, ranging from 12.4 µg L-1 diuron to 187 µg L-1 tebuthiuron. Our results clearly demonstrated that inhibition of ΔF/Fm' in PSII is directly linked to reduced growth (R2 = 0.95) in this species, further supporting application of ΔF/Fm' inhibition as a valid bioindicator of ecological relevance for PSII herbicides that could contribute to deriving future WQGVs. In contrast, SGR and ΔF/Fm' of C. muelleri were nonresponsive to the non-PSII herbicide haloxyfop at the highest concentration tested (4570 µg L-1), suggesting haloxyfop does not pose a risk to C. muelleri. The toxicity thresholds (e.g. no effect concentrations; NECs) identified in this study will contribute to the derivation of high-reliability marine WQGVs for some alternative herbicides detected in GBR waters and support future assessments of the cumulative risks of complex herbicide mixtures commonly detected in coastal waters.

Assessing the toxicity of herbicide isoproturon on Aporrectodea caliginosa (Oligochaeta) and its fate in soil ecosystem.

This study was conducted to determine the residues of isoproturon and its metabolites, 1-(4-isopropylphenyl)-3-methylurea, 1-(4-isopropylphenyl) urea, and 4-isopropylanilin in soil and mature earthworms under laboratory conditions. Mature earthworms (Aporrectodea caliginosa) were exposed for various durations (7, 15, 30, and 60 days) to soils contaminated with isoproturon concentrations (2, 4, 6, 8, and 10 mg kg(-1) soil). The decrease in isoproturon concentration in the soil was inversely correlated to it's initial concentration. The highest concentration detected for isoproturon in earthworms was observed during the first 15 days and decreased thereafter. Acute toxicity of isoproturon was investigated; total soluble protein content and glycogen of the worms were evaluated. Levels of these parameters were related to isoproturon concentration in soil and earthworms. No lethal effect of isoproturon was observed even at the concentration of 1200 mg kg(-1) soil after 60 days of exposure. A reduction of total soluble protein was observed in all treated worms (maximum 59.54%). This study suggests the use of the total soluble protein content and glycogen of earthworms as biomarkers of exposure to isoproturon.

Structure-immunomodulatory activity relationships of Hedysarum polysaccharides extracted by a method involving a complex enzyme combined with ultrasonication.

A new, more effective and environmentally friendly method involving a complex enzyme combined with ultrasonication was employed to extract and isolate three novel polysaccharides (HPS-MCs: HPS-MC, HPS-MC (50%) and HPS-MC (80%)) of Radix Hedysari. Compared with polysaccharides obtained using a traditional extraction method (hot water extraction, HPS-R), the yields and total carbohydrate contents of HPS-MCs were significantly higher. HPS-MC (80%) exhibited relatively strong immunomodulatory activity and a concentration-dependent dose-response relationship under cyclophosphamide (CP)-induced immunosuppressive conditions in mice models. To more comprehensively investigate the relationships between structural characteristics and immunomodulatory activity, HPS-MC (80%) was fractionated into three major homogeneous polysaccharide fractions (HPS-MC (80%)s: HPS-MC (80%)-1, HPS-MC (80%)-2, and HPS-MC (80%)-3). These three homogeneous polysaccharides had different mass percentages of monosaccharides species (rhamnose, arabinose, mannose, glucose, and galactose) by gas chromatography (GC) and different molecular weights and chain conformations by high-performance gel permeation chromatography coupled with multi-angle laser light scattering (HPGPC-MALLS), and promoted macrophage and splenocyte proliferation to different degrees. These findings indicated that HPS-MC (80%) had a prominent potential immune response, especially HPS-MC (80%)-2 and HPS-MC (80%)-3, and might be suitable candidates for functional foods or potential novel immunomodulators.

Estrogenic and anti-androgenic effects of the herbicide tebuthiuron in male Nile tilapia (Oreochromis niloticus).

Tebuthiuron is a phenylurea herbicide widely used in agriculture that can reach the aquatic environments, possibly posing negative effects to the aquatic biota. Phenylurea herbicides, such as diuron, are known to cause estrogenic and anti-androgenic effects in fish, but no such effects were yet reported for tebuthiuron exposure. Thus, the aim of this study was to evaluate if tebuthiuron, at environmentally relevant concentrations (100 and 200ng/L) and after 25days of exposure have estrogenic and/or anti-androgenic effects on male of Nile tilapia (Oreochromis niloticus), through the evaluation of plasmatic testosterone (T) and estradiol (E2) levels, brain aromatase (CYP19) levels (western-blot), and by evaluating the histology of the testicles. When compared to the control group, plasmatic T levels decreased about 76% in the animals exposed to 200ng/L of tebuthiuron, while E2 levels increased about 94%, which could be related to a significant increase (77%) in CYP19A1 levels, an enzyme that catalyzes the conversion of androgens into estrogens. Histological analyses of the testicles also demonstrated that tebuthiuron at both tested concentrations caused a decrease in the diameter of the seminiferous tubules and in the diameter of the lumen. Therefore, the gonadosomatic index (GSI) was reduced by 36% % in the animals exposed 200ng/L to tebuthiuron. Indeed, the relative frequency of spermatocytes and spermatids increased respectively 73% (200ng/L) and 61% (100ng/L) in the tebuthiuron exposed animals, possibly due to the impairment of sperm release into the lumen, that was decreased 93% (200ng/L) in the treated animals compared to the control. These results confirm that tebuthiuron causes estrogenic and anti-androgenic effects in Nile tilapias at environmentally relevant concentrations.

Biochemical effects of nonylphenol polyethoxylate adjuvant, Diquat herbicide and their mixture on the three-spined stickleback (Gasterosteus aculeatus L.).

This study examined the response of 7-ethoxyresorufine-O-deethylase, glutathione-S-transferase, glutathione peroxidase, glutathione content, level of thiobarbituric acid reactive compounds and circulating vitellogenin, in three-spined sticklebacks after 21 days of exposure to Diquat herbicide, commercial nonylphenol polyethoxylate adjuvant and mixture between Diquat and adjuvant. The results showed that adjuvant exerted more important oxidative effects than Diquat and that mixture effects were unlike to single additivity. This study argues for ecotoxicological risk assessment of adjuvants and mixtures of adjuvants and pesticides.

Induction of mouse lung adenomas by amines or ureas plus nitrite and by N-nitroso compounds: effect of ascorbate, gallic acid, thiocyanate, and caffeine.

Lung adenomas were induced in strain A mice by chronic treatment with N-nitroso compounds (given in drinking water) and with amines or ureas in food plus NaNO2 in drinking water. We studied the effects of varying the concentrations of three N-nitroso compounds and NaNO2 concentration in the morpholine plus NaNO2 and methylurea plus NaNO2 systems. Sodium ascorbate (NaASC) at the highest level tested (11.5 or 23 g/kg food) gave 89-98% inhibition of adenoma induction by the NaNO2 plus piperazine, morpholine, and methylurea systems. In 7 groups, NaASC produced increases of 15-59% in adenoma induction by nitrosomorpholine (NM) and mononitrosopiperazine (MNP), possibly because the mice consumed more of the nitrosamine solution. Adenoma induction by morpholine plus NaNO2 was strongly inhibited by gallic acid, moderately inhibited by caffeine, and unaffected by thiocyanate (all added to the food). Gallic acid inhibited or had no effect on the action of NM and MNP. We discussed the proposal that NaASC (or perhaps gallic acid) be administered with readily nitrosatable drugs.

How benthic diatoms within natural communities respond to eight common herbicides with different modes of action.

Herbicides are common pollutants of rivers in agricultural regions. These contaminants include various types of chemicals with different modes of toxic action. Herbicides can have toxic effects on freshwater benthic diatoms, the base of the aquatic food web. We examined the effects of (non-mixture) herbicide exposure to the health of diatoms for eight common herbicides with three different modes of action; the photosystem II (PSII) inhibitors: atrazine, simazine, hexazinone, tebuthiuron and diuron; two auxinic herbicides: MCPA and 2,4-D; and the EPSP synthase inhibitor: glyphosate. Benthic diatoms within riverine communities were exposed to each herbicide in rapid toxicity tests at concentrations of 50, 200 and 500µgL(-1). The most sensitive taxa were Gomphonema spp. and Encyonema gracilis. Navicula cryptotenella was the most tolerant to herbicide exposure. There was no significant effect of the different herbicide modes of action at the community level. Herbicide mode of action did not alter which taxa were most sensitive within the community and sensitivity rankings of the dominant diatom taxa were similar for each of the eight herbicides. The consistency of the results between herbicides suggests that freshwater benthic diatoms may be suitable in situ indicators for detecting the toxicity of herbicides with differing modes of action.

Mutagenic properties of linuron and chlorbromuron evaluated by means of cytogenetic biomarkers in mammalian cell lines.

Agricultural practices are usually supported by several chemical substances, such as herbicides. Linuron and chlorbromuron are phenylurea herbicides largely used to protect crops from weeds, blocking photosynthesis by inhibition of the photosystem II complex. The former, also commercially known as lorox or afalon, is selectively used to protect bean and French bean plants, fennels, and celeriacs; the second, commercially known as maloran, is selectively used for carrots, peas, potatoes, soy sprouts, and sunflowers. Considering the widespread use of herbicides and, more generally, pesticides, it is important to clarify their involvement on human health, one of them concerning the possible direct or indirect effect on the genome of exposed populations. Here, we show that these herbicides are endowed by mutagenic properties, as demonstrated by an increased number of chromosomal aberrations (CAs) in two exposed Chinese hamster cell lines derived from ovary and epithelial liver, respectively. This was also confirmed by sister chromatid exchange (SCE) and micronucleus (MN) assays. Our present and previously obtained data clearly indicate that phenylurea herbicides must be used with great caution, especially for agricultural workers who use large amounts of herbicides during their work, and particular attention should be given to residues of these herbicides and their involvement in environmental pollution.

Effect of isoproturon pretreatment on the biochemical toxicodynamics of anilofos in male rats.

Anilofos and isoproturon are important herbicides of organophosphorus and substituted phenylurea groups, respectively. Isoproturon is an inducer of hepatic drug-metabolizing enzymes. Animals and humans have the potential to be exposed to the mixture of these intentionally introduced environmental xenobiotics, but toxicological interactions between these herbicides are not known. Effects of isoproturon pretreatment (675 mg/kg/day for 3 consecutive days) on the toxic actions of anilofos administered orally as a single dose (850 mg/kg) were evaluated by determining some biochemical attributes in blood (erythrocyte/plasma), brain and liver of rats. Anilofos or isoproturon alone or in combination failed to produce any noticeable signs of cholinergic hyperactivity and behavioural alterations. Isoproturon did not potentiate the anticholinesterase action of anilofos in blood and liver. Inhibition of brain acetylcholinesterase was significantly protected. No significant alteration in anilofos-mediated production of lipid peroxidation was observed in erythrocyte and brain of isoproturon-pretreated rats, but it was significantly increased in liver. Anilofos did not affect GSH and GST. The isoproturon-mediated increase in GSH levels of brain (threefold) and liver (3.6-fold) was also not affected following combined administration. GST activity was increased in liver of rats given isoproturon alone (fourfold) or in combination with anilofos (2.8-fold). Activities of total ATPase, Mg2+-ATPase and Na+-K+-ATPase were not affected in rats given either anilofos alone or herbicides in sequence. With these treatments, there were no alterations in the protein content of plasma, brain and liver. Overall findings of the study indicate that isoproturon pretreatment does not alter the toxicity of anilofos, the GSH-GST metabolic pathway may not have a significant implication in the detoxification of anilofos and the production of a reactive oxygen species may be a factor in mediating anilofos toxicity.

In vitro cytotoxicity and differential cellular sensitivity of derivatives of diamino acids. II. N1-methyl, N1-allyl, N1-(2-chloroethyl) and N1-propargyl nitrosoureas.

The in vitro cytotoxicity and differential cellular sensitivity of a series of new N1-methyl, N1-allyl, N1-2-chloroethyl and N1-propargyl nitrosourea derivatives of diamino acids were determined in the National Cancer Institute's primary antitumor drug screen. The compounds tested showed an in vitro anticancer activity similar to commercialized nitrosoureas such as CCNU, BCNU, MeCCNU, chlorozotocin, streptozotocin and PCNU. The alkylating moiety of the nitrosoureas seems to play a role in the general selectivity of our compounds. The N1-methyl and N1-2-chloroethyl nitrosourea derivatives are more selective for central nervous system cell lines, the N1-allyl nitrosourea derivatives are more selective for lung cancer cell lines and the N1-propargyl nitrosoureas are more selective for leukemia cell lines.

In vitro cytotoxicity and differential cellular sensitivity of derivatives of diamino acids. I. N1-methyl, N1-allyl, N1-(2-chloroethyl) and N1-propargyl ureas.

The in vitro cytotoxicity and differential cellular sensitivity of a series of new N1-methyl, N1-allyl, N1-2-chloroethyl and N1-propargyl urea derivatives of diamino acids were determined in the National Cancer Institute's primary antitumor drug screen. The compounds tested showed an in vitro anticancer activity similar to commercialized nitrosoureas such as CCNU, BCNU, MeCCNU, chlorozotocin, streptozotocin and PCNU. The alkylating moiety of the ureas seems to play a role in the general selectivity of our compounds. The N1-methyl and N1-2-chloroethyl urea derivatives are more selective for central nervous system cell lines and the N1-allyl urea derivatives are more selective for lung cancer cell lines. The N1-propargyl ureas did not show any particular selectivity in the 60 human cell lines tested.

DNA damaging effects of pesticides measured by the single cell gel electrophoresis assay (comet assay) and the chromosomal aberration test, in CHOK1 cells.

One herbicide (isoproturon), two fungicides (carbendazim and chlorothalonil) and etoposide (an effective antitumor agent used as a positive control), were tested for their ability to induce cytotoxic and genotoxic effects in Chinese Hamster Ovary (CHOK1) cells. Etoposide induced DNA damage detectable both by the alkaline Single Cell Gel Electrophoresis (SCGE) assay and the chromosomal aberration (CA) test in absence of noticeable cytotoxicity. With the SCGE assay, a clear induction of DNA damage was observed for chlorothalonil within a 0.2 to 1 microM concentration range. In the CA test, chlorothalonil gave also positive results, inducing mainly chromosome breaks. In contrast, no DNA damage was observed with the SCGE assay for carbendazim and isoproturon. In the CA test, carbendazim induced only numerical aberrations in the concentration range of 25 microM to 100 microM, and isoproturon did not induce any significant increase in CA. In conclusion, chlorothalonil appears genotoxic in proliferative CHOK1 cells, and as expected, the aneugenic compound, carbendazim, did not induce DNA strand breaks in the SCGE assay.

Mutagenicity of N,N'-dimethylurea and methylamine hydrochloride in the Ames Salmonella/microsome test: absence of mutagenic response.

Methyl isocyanate (MIC) in aqueous solution forms methylamine (MA) and N,N'-dimethylurea (DMU). MA in buffered system further converts into its salt form, methylamine hydrochloride (MAH). Therefore, MAH and DMU were evaluated for their mutagenic activity in the in vitro Ames Salmonella/microsome mutagenicity test. The liquid preincubation protocol was followed, using tester strains TA98, TA100 and TA104 of Salmonella typhimurium, in the presence of 0, 5, 15 and 30% Aroclor 1254-induced rat liver S9 mixture. DMU and MAH did not induce a mutagenic response in any of the tester strains, both in the presence and in the absence of S9 mixture. The results therefore confirm that MIC in its native form or as its unknown metabolites is responsible for the mutagenic activity reported earlier by us in the his tester strains TA100 and TA104 of Salmonella typhimurium (Mutation Res., 204 (1988) 123-129) and not due to its hydrolysis products, MA or DMU.

Individual susceptibility of mice to a mutagen in both germ and somatic cells.

Male Swiss mice received simultaneously, by gavage, 500 mg methylurea/kg body weight and 25 mg sodium nitrite/kg body weight, and in a further experiment 330 mg of methylurea/kg and 17 mg sodium nitrite/kg, for 5 consecutive days. This treatment resulted in a dose-dependent mutagenic effect in both the dominant-lethal and the micro-nucleus tests. Furthermore, in both mammalian tests, some animals were more susceptible to the mutagenic compounds than were others. However, the liver microsomal metabolizing system did not seem to be responsible for this variation of mutagenic induction.

Analysis of the in vivo nitrosation capacity of the larvae used in the wing somatic mutation and recombination test of Drosophila melanogaster.

The in vivo nitrosation capacity of third-instar larvae of Drosophila melanogaster was assessed using the wing somatic mutation and recombination test (SMART). Larvate derived from two different crosses, the standard cross (ST) and the high bioactivation cross (HB) both involving the recessive wing cell markers multiple wing hairs (mwh) and flare (flr3), were used. The HB cross is characterised by an increased cytochrome P450-dependent bioactivation capacity for promutagens and procarcinogens. The larvae were treated either with methyl urea, sodium nitrite or its combination. N-Nitrosomethylurea was used as a positive control. The wings of the resulting flies were analysed for the occurrence of mutant spots produced by various types of mutational events or by mitotic recombination. Methyl urea is negative in the ST and the HB cross, whereas sodium nitrite is weakly genotoxic in both crosses. However, the combination of both compounds produces highly increased frequencies of mutations and recombinations predominantly in the HB cross. The genotoxic effects produced by the combined treatments were considerably increased when mashed potatoes or an agar-yeast medium were used for the treatment instead of the standard instant medium. Treatment of larvae with the mixture resulting from the in vitro reaction of nitrosation precursors also resulted in high frequencies of induced spots comparable to those recorded with the potent genotoxin N-nitrosomethylurea. Further experiments showed that the genotoxic effect resulting from the in vivo exposure to nitrosation precursors can be reduced by co-treatment with catechin, a known nitrosation inhibitor. The present study demonstrates that the wing spot test is well suited for the determination of genotoxicity produced by in vivo nitrosation processes and for the study of their modulation by individual compounds or dietary complex mixtures.

Effects of the formaldehyde releasing preservatives dimethylol urea and diazolidinyl urea in several short-term genotoxicity tests.

The two formaldehyde (FA)-releasers dimethylol urea (DMU) and diazolidinyl urea (DZU) are widely used as preservatives or additives. They were tested for genotoxicity in three short-term test systems, i.e. in the Salmonella typhimurium mutagenicity assay, in the in vitro micronucleus test with V79 Chinese hamster cells and in the in vitro tubulin assembly assay using isolated tubulin from pig brains. The polymerization products obtained in the tubulin assembly assay were examined additionally by electron microscopy. In the S. typhimurium mutagenicity assay with the pre-incubation assay both FA-releasers tested show a clear and concentration-dependent increase in the number of revertants in strains TA98, TA100 and TA102 with and without metabolic activation (rat liver S9 mix). In all cases, a biologically relevant increase in the number of revertants was achieved within the concentration range tested (DZU: 0.04-1.8 micromol per plate, DMU: 0.21-8.33 micromol per plate). FA was tested at 0.06-2.5 micromol per plate and lead to similar effects.Both compounds induce the formation of micronuclei (concentration range tested: DZU: 2.5-50 micromol/l, DMU: 3.3-333 micromol/l). However, DMU shows a comparatively weaker effect exclusively in the absence of the metabolizing enzymes. By contrast, DZU yields a distinct increase of the micronucleus rate in the absence and in the presence of S9. In addition, DZU predominantly causes an increase of large micronuclei, which suggests that this compound has a marked aneugenic potential. Cytotoxic effects accompany the clastogenic effects of both DMU and DZU. The examination of DMU and DZU in view of a possible aneugenic potential in the tubulin assembly assay yielded the following results: DMU at concentrations up to 10 mmol/l did not influence the formation of microtubuli, whereas DZU inhibited this process completely at 3 mmol/l. FA at 6 mmol/l completely inhibited the tubulin assembly. These results could clearly be confirmed by electron microscopy examination. The different potential of the two compounds with respect to the inhibition of tubulin formation is apparently due to a significant difference in the degree of FA release. According to these results, both compounds have to be considered as genotoxic in vitro. On account of these data and because of the widespread use of these two compounds in various products used in daily life, a reevaluation of the risk associated with these compounds seems to be necessary.

Antimutagenic effect of one variety of green pepper (Capsicum spp.) and its possible interference with the nitrosation process.

It is known that the poblano green pepper, a significant component in the Mexican diet, contains certain natural compounds such as chlorophyll, beta-carotene, and vitamins, which have antimutagenic and/or anticarcinogenic properties. Using the somatic mutation and recombination test in wing cells of Drosophila melanogaster, an extract of the poblano pepper (Capsicum spp.) was evaluated to determine its antimutagenic effect against the nitrosation process, simulating the process occurring in the human stomach caused by known food additives. Larvae of 72h old D. melanogaster of standard (ST) and high bioactivation (HB) crosses were exposed in a simultaneous, chronic treatment with the juice expressed from the crushed, whole, fresh pepper fruit, plus the mixture of 20mM methyl urea (MU) and sodium nitrite (SN), mixed with the animals' food. Three doses of pepper juice (12.5, 25, and 50%) were used. The background mutation rate given as spots per wing was 0.36 and 0.48 for ST and HB, respectively. Mutation frequencies produced by the MU and SN mixture was 1.73 (ST) and 26.46 (HB) mutations per wing. The poblano juice decreased the above rates between 40 and 80%, respectively. The experiments suggest that some compounds present in the green pepper may cause this antimutagenic effect by interfering with the nitrosation process. The role of the extract and one of its components, such as vitamin C, in the nitrosation process will be discussed.

Haemotoxic effect of phenylurea herbicides in rats: role of haemoglobin-adduct formation in splenic toxicity.

Three substituted phenylurea herbicides were used for the study of the haemotoxic effects on rats of chronic exposure to these compounds. Female Sprague-Dawley rats were given monuron, diuron or fenuron (250-1000 mg/kg diet) for 14 months. The final body weights were similar to those of controls. No treatment-related effects on organ weights were observed at autopsy, except for a dose-related increase in spleen weights in rats treated with monuron or diuron, but not in those treated with fenuron. The proportion of haemoglobin in the form of methaemoglobin increased in the dosed group and resulted in a secondary anaemia with changes in the morphology of erythrocytes. Haemoglobin adducts of aromatic amines released from the herbicides were present at dose-related levels in rats treated with monuron or diuron. Compound-related lesions were observed histologically in treated rats, with increased pigmentation (haemosiderin) in the spleen, reflecting the response to the haemolytic anaemia and methaemoglobinaemia induced by the herbicides. Pigment deposition consisting of golden brown granules in the cytoplasm of the tubular epithelium in the kidney and in the Kupffer cells in the liver were observed only in rats treated with monuron. The haemotoxic effects that were observed may indicate that the formation of adducts between haemoglobin and the parent aromatic amines released metabolically from these herbicides has a role in the splenic toxicity of these compounds.

Determination photostability of selected agrochemicals in water and soil.

The photolysis of selected pesticides in aqueous solutions has been investigated. The photolysis produced different intermediate substances, which were also found to be soil and microbial degradation products. The phototransformation in the presence of TiO2 and humic substances leads to a disappearance of these compounds. The reaction rate is dependent on the semiconductor oxide and concentration. Photoproducts were isolated and characterized by different spectroscopic methods. Results from this study indicate that degradation products of isoproturon are more toxic on Daphnia magna than on the parent compound.