Effects of 2-bromopropane on the female reproductive function in Sprague-Dawley rats

Carcinogenicity and testicular toxicity of 2-bromopropane in a 26-week inhalation study using the rasH2 mouse model

2-Bromopropane (2-BP) is a colorless liquid at room temperature and is used in closed systems in factories, mainly as an intermediate for medicines, pesticides, and other chemicals. However, the carcinogenicity of 2-BP is still unknown. The CByB6F1-Tg(HRAS)2Jic (rasH2) transgenic mouse model has been established as an alternative to long-term studies (1.5 years-lifetime) to detect carcinogenicity in as short a time as six months. We performed a 26-week inhalation exposure study of 2-BP using the rasH2 mouse model. Male and female rasH2 mice were exposed to 0, 67, 200, or 600 ppm of 2-BP for 6 h/day, 5 days/week for 26 weeks. All tissues and blood were collected and subjected to biological and histopathological analyses. The results showed a concentration-dependent increase in lung tumor development in male and female rasH2 mice exposed by inhalation to 2-BP, which was significant by Peto's and Poly-3 trend tests. Furthermore, in male rasH2 mice, 2-BP was found to be a testicular toxin. This study is the first to demonstrate that 2-BP is carcinogenic in male and female mice and a testicular toxin in male mice using the rasH2 mouse model.

Occupational exposure to neurotoxic substances in Asian countries - challenges and approaches

The fact that a conference on neurotoxicity was held in China triggered the idea to provide an insight into occupational diseases, their development and the approaches to investigate them in Asian countries. A historical review, a meta-analysis, and studies on humans and animals provide impressions on past and current problems. The Korean example showed that each newly introduced industry is accompanied by its own problems as regards occupational diseases. Mercury and carbon disulfide were of importance in the beginning, whereas solvents and manganese became important later. Outbreaks of diseases were important reasons to guide both the public and the governmental attention to prevention and allowed within a relatively short time considerable progress. As the example on the replacement of 2-bromopropane by 1-bromopropane showed, also the introduction of chemicals that are more beneficial for the environment may result in additional occupational risks. A lower mutagenicity of 1-bromopopane was shown to be associated with a greater neurotoxicity in Japanese studies. Although occupational health and diseases are commonly related to adults, child workers exposed to solvents were examined in a Lebanese study. The study started outlining the health hazards in young workers because they might be at a much greater risk due to the not yet completed maturation of their nervous system. That some occupational diseases are not yet a focus of prevention was shown by the study on pesticides. If at all, the serious health consequences resulting from excessive exposure were investigated. Research enabling precautionary actions was not available from the international literature. Despite globalization the knowledge on occupational diseases is not yet "globalized" and each country obviously undergoes its own development triggered by local experiences. Economic development that requires a healthy workforce, but also public interest that challenges governmental regulations further efforts on the prevention of occupational diseases. The paper reflects a summary of the talks presented at the symposium "Occupational Neurotoxicities in Asian Countries" as part of the 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health.

Occupational reproductive function abnormalities and bladder cancer in Korea

The purpose of this study was to review occupational reproductive abnormalities and occupational bladder cancer in Korea and to discuss their toxicological implications. Reproductive dysfunction as a result of 2-bromopropane poisoning was first reported in Korean workers. In 1995, 23 of the 33 workers (25 female and 8 male workers) who were exposed to 2-bromopropane during the assembly of tactile switch parts developed reproductive and/or hematopoietic disorders. A total of 17 (68%) workers were diagnosed with ovarian failure. Two of the eight male workers experienced azoospermia and four workers experienced some degree of oligospermia or reduced sperm motility. In summary, 2-bromopropane poisoning caused severe reproductive effects in Korean workers. The prognosis was poor for reproductive dysfunction. A few cases of occupational bladder cancer have been reported in Korea, whereas other cancers of the urinary tract have not been reported after occupational exposure. A few cases of benzidine-induced cancer have been reported in Korea and 592 workers in Japan have received compensation for benzidine and β-naphthylamine-induced cancer. In conclusion, a few cases of benzidine-induced occupational bladder cancer have been reported in Korea. However, benzidine-induced bladder cancer will likely be an important occupational health issue in Korea in the coming years.

Apoptosis contributes to testicular toxicity induced by two isomers of bromopropanes

The aim of this study was to investigate the different testicular toxicity and the role of apoptosis in the possible mechanism induced by the two isomers of bromopropanes (BPs) in the same dosage. Following the 14-day treatment with a single dose of 1-BP and 2-BP (1 g/kg), male rats were killed and a series of experiments were performed. 1-BP and 2-BP both significantly decreased the epididymal sperm count, while only 2-BP induced an increase in sperms with abnormal heads. Morphological evaluation showed that 1-BP did not cause morphological changes in seminiferous epithelium, but 2-BP treatment resulted in the disappearance of spermatogonia, atrophy of the seminiferous tubules and degeneration of germ cells. 2-BP significantly increased the TUNEL-positive cells and the activation of caspase-3 and decreased the genes and proteins expression of Bax, Bcl-2 and p53. In contrast, there were no significant changes in the expression of apoptosis-related genes and proteins in 1-BP group, though the TUNEL-positive cells were significantly increased. Taken together, this study indicated that those two isomers both have toxicity in male rats, however, the testicular toxicity and the role of apoptosis in the toxic mechanism induced by 1-BP and 2-BP may be different.

Transfer of occupational health problems from a developed to a developing country: lessons from the Japan-South Korea experience

Many corporations move their manufacturing facilities or technologies from developed to developing countries. Stringent regulations have made it costly for industries to operate in developed, industrialized countries. In addition, labor costs are high in these countries, and there is increasing awareness among the general public of the health risks associated with industry. The relocation of hazardous industries to developing countries is driven by economic considerations: high unemployment, a cheaper labor force, lack of regulation, and poor enforcement of any existing regulations make certain countries attractive to business. The transfer of certain industries from Japan to Korea has also brought both documented occupational diseases and a new occupational disease caused by chemicals without established toxicities. Typical examples of documented occupational diseases are carbon disulfide poisoning in the rayon manufacturing industry, bladder cancer in the benzidine industry, and mesothelioma in the asbestos industry. A new occupational disease due to a chemical without established toxicities is 2-bromopropane poisoning. These examples suggest that counter-measures are needed to prevent the transfer of occupational health problems from a developed to a developing country. Corporate social responsibility should be emphasized, close inter-governmental collaboration is necessary and cooperation among non-governmental organizations is helpful.

Strengths and limitations of using repeat-dose toxicity studies to predict effects on fertility

The upcoming European chemicals legislation REACH (Registration, Evaluation, and Authorisation of Chemicals) will require the risk assessment of many thousands of chemicals. It is therefore necessary to develop intelligent testing strategies to ensure that chemicals of concern are identified whilst minimising the testing of chemicals using animals. Xenobiotics may perturb the reproductive cycle, and for this reason several reproductive studies are recommended under REACH. One of the endpoints assessed in this battery of tests is mating performance and fertility. Animal tests that address this endpoint use a relatively large number of animals and are also costly in terms of resource, time, and money. If it can be shown that data from non-reproductive studies such as in-vitro or repeat-dose toxicity tests are capable of generating reliable alerts for effects on fertility then some animal testing may be avoided. Available rat sub-chronic and fertility data for 44 chemicals that have been classified by the European Union as toxic to fertility were therefore analysed for concordance of effects. Because it was considered appropriate to read across data for some chemicals these data sets were considered relevant for 73 of the 102 chemicals currently classified as toxic to reproduction (fertility) under this system. For all but 5 of these chemicals it was considered that a well-performed sub-chronic toxicity study would have detected pathology in the male, and in some cases, the female reproductive tract. Three showed evidence of direct interaction with oestrogen or androgen receptors (linuron, nonylphenol, and fenarimol). The remaining chemicals (quinomethionate and azafenidin) act by modes of action that do not require direct interaction with steroid receptors. However, both these materials caused in-utero deaths in pre-natal developmental toxicity studies, and the relatively low NOAELs and the nature of the hazard identified in the sub-chronic tests provides an alert for possible effects on fertility (or early embryonic development), the biological significance of which can be ascertained in a littering (e.g. 2-generation) study. From the chemicals reviewed it would appear that where there are no alerts from a repeat-dose toxicity study, a pre-natal developmental toxicity study and sex steroid receptor binding assays, there exists a low priority for animal studies to address the fertility endpoint. The ability for these types of tests to provide alerts for effects on fertility is clearly dependent on the mode of action of the toxicant in question. Further work should therefore be performed to determine the 'failure rate' of this type of approach when applied to a larger group of chemicals with diverse modes of action.

Neuro-reproductive toxicities of 1-bromopropane and 2-bromopropane

2-Bromopropane was used as an alternative to chlorofluorocarbons in a Korean electronics factory and caused reproductive and hematopoietic disorders in male and female workers. This causality was revealed by animal studies, and target cells were identified in subsequent studies. After identification of 2-bromopropane toxicity, 1-bromopropane was introduced to the workplace as a new alternative to ozone-depleting solvents. 1-Bromopropane was considered less mutagenic than 2-bromopropane, but, in contrast, animal experiments revealed that 1-bromopropane is a potent neurotoxic compound compared with 2-bromopropane. It was also revealed that 1-bromopropane has reproductive toxicity, but the target cells are different from those of 2-bromopropane. Exposure to 1-bromopropane inhibits spermiation in male rats and disrupts the development of follicles in female rats, in contrast to 2-bromopropane, which targets spermatogonia and oocytes in primordial follicles. After the first animal study describing the neurotoxicity of 1-bromopropane, human cases were reported. Those cases showed decreased sensation of vibration and perception, paresthesia in the lower extremities, decreased sensation in the ventral aspects of the thighs and gluteal regions, stumbling and headache, as well as mucosal irritation, as the initial symptoms. The dose-response of bromopropanes in humans and mechanism(s) underlying the differences in the toxic effects of the two bromopropanes remain to be determined.

Developmental effects of inhalation exposure to 2-bromopropane in rats

2-Bromopropane (2-BP), known as a reproductive and hematopoietic toxicant in humans, was assessed for developmental toxicity. Sprague-Dawley rats were exposed by inhalation to 2-BP at a concentration of 0 (control), 125, 250, 500, or 1000 ppm for 6 h per day, 7 days per week during 2 weeks of the pre-mating period, during the mating period until copulation and during the period of gestation days 0-19. After parturition, dams were allowed to breast feed their pups until postnatal day 4. 2-BP exposure resulted in no signs of maternal toxicity as assessed by clinical observations and body weight gain. On the other hand, the inhalation exposure to 1000 ppm markedly decreased the number of pups born, although the number of implantations did not decrease. No effect of 2-BP on pups weights or survival until postnatal day 4 was found. It was found that the repeated inhalation exposure of rats to 1000 ppm 2-BP induced fetal lethality during the post-implantation period.

A survey on exposure level, health status, and biomarkers in workers exposed to 1-bromopropane

BACKGROUND

The aim of this study was to evaluate the health effects of exposure mainly to 1-bromopropane, which is an alternative to ozone-depleting solvents, and to establish biomarkers for assessing 1-bromopropane exposure.

METHODS

Twenty-four female and 13 male workers of a 1-bromopropane-factory were interviewed, and their urine and blood samples were collected. Measured parameters included 1-bromopropane levels in the factory, as well as individual exposure levels, urinary 1-bromopropane levels, enzymatic activity and M subunit's concentration of serum creatine kinase (CK).

RESULTS

Frequent symptoms reported by workers exposed to 1-bromopropane were nose, throat, and eyes irritation or malaise and/or headache. Urinary 1-bromopropane levels correlated significantly with individual exposure levels, but enzymatic activity or CK-M subunit did not.

CONCLUSIONS

The symptoms suggested irritation of the mucous membrane and possible adverse effects on the central nervous system. There were no severe chronic symptoms suggestive of neurological damage in workers exposed to less than 170 ppm. Urinary 1-bromopropane level may be a good indicator of exposure. Am. J. Ind. Med. 45:63-75, 2004.

Acute effects of 2-bromopropane and 1,2-dibromopropane on hepatotoxic and immunotoxic parameters in female BALB/c mice

In the present studies, the acute toxic effects of 2-bromopropane (2-BP) and its analog, 1,2-dibromopropane (1,2-DBP), were investigated in female BALB/c mice. The mice were treated orally with either 2-BP at 2000 and 4000 mg/kg or 1,2-DBP at 300 and 600 mg/kg. Four days before necropsy, the mice were immunized intraperitoneally with sheep red blood cells (SRBCs). 1,2-DBP reduced the weights of the spleen and thymus weights and decreased the number of splenic cells. In addition, treatment with 1,2-DBP suppressed the antibody response to SRBCs. Meanwhile, only the antibody response was significantly suppressed by treatment with 2-BP. In the subsequent studies, the time course effects of 2-BP and 1,2-DBP on the hepatotoxic parameters were compared in female BALB/c mice. When mice were treated orally with either one of these chemicals for 6, 12, 24 and 48 h, the activities of serum alanine aminotransferase and aspartate aminotransferase elevated significantly only with 1,2-DBP 24 h after the treatment. The hepatic content of glutathione was reduced by 1,2-DBP. Meanwhile, these parameters were increased by 2-BP. The present results suggest that 1,2-DBP in the Solvent 5200 also contributes to the immnunotoxicity, although 2-BP is a major component.

Impairment of male rat reproductive function in F1 offspring from dams exposed to 2-bromopropane during gestation and lactation

The toxic effects of 2-bromopropane (2-BP) on the reproductive tracts of male F1 offspring from dams exposed to 2-BP during gestation and lactation were investigated. Ten pregnant (sperm-positive) Sprague-Dawley rats per group were exposed sc to 2-BP at 135, 405, and 1215 mg/kg/day from gestation day (GD) 6 to postnatal day (PND) 20. 2-BP decreased the proportion of dams littering at the two highest doses. At the highest dose, the rate of delivery and surviving pups were significantly lower than in the controls (P < or = 0.05). The relative weights of testes vs. brain were significantly lower than the controls (P < or = 0.05) on PND 33 and 63 at 405 mg/kg/day, and on PND 90 at 1215 mg/kg/day in the F1 rats. Seminiferous tubule atrophy, germ cell loss, and increased Leydig cell proliferation were observed at the highest dose by histopathologic examination. Female offspring has a decrease in all follicle types at the high dose. These results suggest that gestational and lactational exposure to 2-BP at a high maternally toxic dose impairs the development of the reproductive organs of the offspring.

Immunotoxic effects of 2-bromopropane in male Sprague-Dawley rats: a 28-day exposure study

Immunotoxic effects of 2-bromopropane were investigated in male Sprague-Dawley rats. The rats were treated orally daily with 2-bromopropane at 100, 330, or 1000 mg/kg for 28 consecutive days. Four days before necropsy, the rats were immunized intravenously with sheep red blood cells (SRBCs). The body and thymus weights were significantly reduced by treatment with 2-bromopropane at the highest dose. In addition, the numbers of splenic and thymic cells were decreased by 2-bromopropane. In hematology, the numbers of white blood cells, red blood cells, and platelets were significantly reduced. Among the serum clinical parameters, the levels of chloride ion were significantly increased by 2-bromopropane. The antibody response to SRBCs was significantly suppressed at the highest dose. With immunized animals, immunophenotyping of splenic and thymic cells was performed to investigate the changes of the number of macrophages, B cells, and T cells in spleen and the number of CD4+ and CD8+ cells in thymus. The numbers of most cell types were significantly decreased in the spleen when animals were treated with 2-bromopropane at 1,000 mg/kg. Likewise, all cell types of thymus were significantly decreased by 2-bromopropane. The present results suggest that 2-bromopropane may have an immunotoxic potential in male Sprague-Dawley rats when the rats are exposed for 28 d.

Synthesis, characterization and in vtro identification of N7-guanine adduct of 2-bromopropane

Recently, we have reported that 2-bromopropane might have an immunotoxic potential in rats when exposed for 28 days. In the present studies, the possibility of 2i-deoxyguanosine adduct formation by 2-bromopropane was investigated in vitro to elucidate molecular mechanism of 2-bromopropane-induced immunosuppression. N7-Guanine adduct of 2'-bromopropane (i.e., N7-isopropyl guanine) was chemically synthesized and structurally characterized by analysis of UV, 1H-NMR, '3C-NMR, COSY and fast atom bombardment mass spectrometry to use as a reference material. Incubation of 2'-deoxyguanosine with an excess amount of 2-bromopropane in PBS buffer solution, pH 7.4, at 37 degrees C for 16 h, followed by a thermal hydrolysis, produced a detectable amount of N7-isopropyl guanine by an HPLC and UV analysis. The present results suggest that 2-bromopropane might form a DNA adduct in N7 position of 2'-deoxyguanosine at a physiological condition.

Effects of 1-bromopropane, 2-bromopropane, and 1,2-dichloropropane on the estrous cycle and ovulation in F344 rats

The present study was performed to investigate comparatively the toxic effects of inhalation exposure of 1-bromopropane, 2-bromopropane, and 1,2-dichloropropane on reproductive physiology, particularly on the estrous cycle and spontaneous ovulation in female F344 rats. The rats received inhalation exposure to different halogenated propanes, and were exposed daily for 8 h throughout almost 3 weeks to 0,50,200 and 1000 ppm of 1-bromopropane or 2-bromopropane, or to 0,50,100 and 200 ppm of 1,2-dichloropropane. Throughout the exposure period of 1-bromopropane or 2-bromopropane, the ratio of the number of estrous cycle of 6 days or longer to the number of all cycles in both 1000 ppm groups were about two-fold the ratio in each control group, however, no significant difference was found between the ratios of exposed and control groups. The ratios of such long estrous cycles in groups exposed to 100 or 200 ppm of 1,2-dichloropropane were six- to seven-fold higher than that of the control group. These ratios in exposed rats differed significantly from those of controls. The number of ovulated ova in rats exposed to 1,2-dichloropropane decreased in a dose-dependent manner, and the number of ovulated ova in the 200 ppm group was significantly different from that of control rats. Such significant changes in ovulation were not observed in rats exposed to 1-bromopropane or 2-bromopropane. The absolute and relative weights of the ovaries and uterus in rats exposed to three halogenated propanes were not significantly different from those in each control. Therefore, the present study clarified that: (1) 1,2-dichloropropane prolonged the length of the estrous cycle and inhibited spontaneous ovulation in F344 rats; and (2) the potency of 1,2-dichloropropane to disturb the female reproductive physiology appeared to be greater compared with that of 1-bromopropane and 2-bromopropane under the present conditions of inhalation exposure.

Involvement of Bcl-2 family genes and Fas signaling system in primary and secondary male germ cell apoptosis induced by 2-bromopropane in rat

Epidemiological surveys and animal experimental studies suggest that exposure to 2-bromopropane (2-BP) could result in reproductive and hematopoietic disorders. The objectives of this study were to investigate the role of apoptosis in 2-BP-induced testicular toxicity and whether this process involves Bcl-2 family genes and the Fas signaling system. Rats were injected percutaneously with 1350 mg/kg 2-BP for 1 to 5 days and then were euthanized at 6 or 12 h after one dose, 6 h after two, three, or five doses, and 2 or 9 days after the final treatment. Light and electron microscopic analyses, TUNEL staining of DNA fragments, agarose gel electrophoresis of low-molecular-weight DNA, and Western blotting analysis of Bcl-2 family proteins and Fas receptor and ligand were conducted. Two-day treatment resulted in selective degeneration of spermatogonia with marked nuclear chromatin condensation. DNA ladder formation on the agarose gel further validated the findings of TUNEL-stained apoptotic cells. The percentage of apoptotic-positive tubules and apoptotic cell index increased time dependently. 2-BP treatment resulted in two distinct morphological changes: an immediate effect on spermatogonia and secondary apoptosis of spermatocytes 9 days after treatment. Downregulation of Bcl-2 after the first or second injection of 2-BP and upregulation of Bax after the first treatment contributed to the initiation of primary apoptosis of spermatogonia. Expression of FasL was inhibited while expression of Fas increased after the 2-BP treatment and remained at levels about two times of the control. However, it increased about sixfold of the control by day 9 after final injection, which contributed to the induction of secondary apoptosis of spermatocytes. Our results indicate that 2-BP resulted in apoptotic death of testicular germ cells and that this process involves the Bcl-2 family genes and the Fas signaling system.

Induction of micronuclei formation in preimplantation mouse embryos after maternal treatment with 2-bromopropane

We examined effects of 2-bromopropane (2-BP), a chlorofluorocarbon replacement, on mouse embryonic mutagenicity. 2-BP was administered to pregnant mice intraperitoneally (i.p.) (300, 600, 900, and 1800 mg/kg) during the early preimplantation period. On day 3 of gestation, micronuclei (MN) frequency and embryo cell number were determined. 2-BP induced a dose-related significant increase in MN frequency and a treatment-related decrease in embryo cell number. Furthermore, the cell numbers were significantly smaller in the MN-positive embryos by two-way ANOVA taking it into account an interactive effect between 2-BP dose and the presence or absence of MN. A simultaneous decrease in cell number and increase in MN frequency may reflect an embryonic developmental disadvantage resulting from maternal treatment with 2-BP. Further study is needed to establish how 2-BP contributes to postimplantation embryonic development.

Influence of 2-bromopropane on reproductive system--short-term administration of 2-bromopropane inhibits ovulation in F344 rats

The present study was performed to investigate the toxic effects of 2-bromopropane (2BP) on the female reproductive system. Female F344 rats were administered 2BP (500 or 1000 mg/kg, i.p.) at intervals of 2 or 3 days for 15-17 days. The body weights were measured and estrous stages were observed throughout the experimental period. Ovulation, organ weights, ovarian histology, and blood biochemistry were investigated on the terminal day of the experiment. Uterine weights in rats treated with 2BP were significantly lower than those in control animals. Body, liver, kidney, and adrenal weights in 2BP-treated rats showed no significant differences from control values. 2BP treatment prolonged estrous cycles and decreased the number of ovulated ova in spontaneous ovulation. In addition, histological examinations showed that the preovulatory follicles in the ovary were altered markedly in 2BP groups. These results show that even in short-term treatment, 2BP injured the ovary, particularly the preovulatory follicles. It appears that these damages of the preovulatory follicles induced by 2BP reduced the numbers of spontaneously ovulated ova in female F344 rats.

2-Bromopropane causes ovarian dysfunction by damaging primordial follicles and their oocytes in female rats

Ovarian dysfunction induced by 2-bromopropane (2-BP) has been described in female factory workers and experimental animals. However, the underlying mechanism is still unclear. To establish the reproductive target site and define mechanisms of 2-BP toxicity in adult female rats, we examined the effects of different doses and duration of exposure to 2-BP in female rats. In the dose-dependent experiments, female rats were exposed to 2-BP at 100, 300, or 1000 ppm or fresh air (n = 9 each) in exposure chambers for 8 h/day for 9 weeks. In the time-course experiments, female rats were exposed to 2-BP at 3000 ppm for 8 h (n = 7 each). The rats were then euthanized 1, 3, 5, and 17 days after exposure. Differential follicle counts and in situ terminal deoxynucleotidyl transferase assay were used to evaluate 2-BP effect on primordial, growing, and antral follicles. Exposure to 2-BP at 300 and 1000 ppm produced a significant reduction in the percentage of primordial, growing, and antral follicles in a dose-dependent manner. Significant reduction in the percentage of primordial follicles at 17 days after exposure was observed in time-course experiments. Exposure to 2-BP at 3000 ppm for 8 h resulted in histological changes in primordial follicles complex at 5 and 17 days after exposure. These changes consisted of distortion of the symmetry of oocytes and their nuclei at Day 5 after exposure and appearance of eccentric pyknotic cells and shrinkage of oocyte nuclei at Day 17 after exposure. In situ end labeling showed increased numbers of apoptotic oocytes and granulosa cells in primordial follicles at Days 5 and 17 after exposure. Our results suggested that ovarian dysfunction induced by 2-BP was caused by the destruction of primordial follicle and its oocyte due to the induction of apoptosis. Our studies also show that the follicle differential count is a more sensitive method than the vaginal smear in monitoring the female reproductive disorders induced by 2-BP.

Assessment of the U.S. Environmental Protection Agency methods for identification of hazards to developing organisms, Part I: The reproduction and fertility testing guidelines

BACKGROUND

Successful reproduction depends on the coordination of many processes, particularly the normal development and subsequent maturation of the sexual organs. The Food Quality Protection Act of 1996 mandates that the U.S. Environmental Protection Agency must protect infants and children from the effects of toxins, including those that affect the reproductive system. Therefore, the Agency finds itself at a critical juncture to make sure that the methods it requires for toxicity testing, the Health Effects Test Guidelines or Series 870 Guidelines, are adequate to determine possible toxicity to children.

METHODS AND RESULTS

We found that two testing protocols included in the core guidelines assess toxicological effects on developing animals. This article aims to provide a detailed analysis of the protocols included in the Reproduction and Fertility Effects Test Guideline. An accompanying article assesses the Developmental Toxicity Testing Guideline. We conducted this analysis on the basis of whether the test would yield the information needed to adequately determine risk to infants and children.

CONCLUSIONS

Our analysis concludes that given the limitations inherent in testing for reproduction and fertility effects during development, it is necessary to include a safety factor during risk assessment of chemicals. This action will fulfill the mandate expressed in the FQPA to protect infants and children from environmental hazards.

Occupational health survey on workers exposed to 2-bromopropane at low concentrations

BACKGROUND

Recent case studies in Korea and animal studies revealed the reproductive and hematopoietic toxicity of 2-bromopropane introduced into workplaces as an alternative to ozone-layer depleting chlorofluorocarbons. We aimed to clarify the dose-effect relationship of 2-bromopropane in workers.

METHOD

The exposure concentration of 2-bromopropane and hematological indices, hormonal levels, menstruation status, and sperm indices were examined in 25 workers (11 males, 14 females) at a 2-bromopropane factory. Regression analyses of the examined indices against time-weighted average (TWA) of exposure concentration were conducted.

RESULTS

Amenorrhea or polymenorrhea was observed only in older females. Hematological indices had a significant relation with TWA of exposure concentration in females with normal menstruation. However, no other indices showed any significant relation with TWA of 2-bromopropane.

CONCLUSIONS

No severe cases of reproductive or hematopoietic disorders were found at less than 10 ppm (TWA), but a possible adverse effect of 2-bromopropane on hematopoiesis could not be disproved.

Effects of 2-bromopropane on spermatogenesis in the Sprague-Dawley rat

In 1995, 2-bromopropane (2-BP) was associated with occupational reproductive and hematopoietic toxicity in Korea. The effect of 2-BP on spermatogenesis, or Leydig cells, has not been determined in adult rats. In the present study, 40 ten-week-old Sprague-Dawley (SD) rats were treated orally with 3.5 g/kg/d of 2-BP for 3 consecutive days. At 1, 3, 5, 7, 14, 28, 42, and 70 d after treatment, testes were perfused with Karnovsky's solution or immersed in Bouin's solution, embedded in plastic or Epon and evaluated with light and electron microscopy. DNA ploidy distributions of testicular suspensions were determined by flow cytometry, which allowed comparison of quantitative spermatogenesis with histopathologic observations. Degeneration of spermatogonia was observed during Stages I-IV in seminiferous tubules on Day 1 after treatment. Spermatocytes, spermatids, Sertoli cells, and Leydig cells appeared normal in the early stage of the study. Whereas spermatid retention in Stages IX-XI was observed on Day 7 after treatment, depletion of spermatocytes and spermatids continued over time, followed by a marked increase of germ cells on Day 42 after treatment. However, the seminiferous tubules did not completely recover by study termination. Leydig cell cellularity increased mildly without any significant morphologic modification at the end of the study. Immunohistochemistry using an antibody against proliferating cell nuclear antigen (PCNA), showed an increased number of immunoreactive Leydig cells in the interstitium. In the flow cytometry analysis, proportions of diploid and tetraploid cells gradually decreased time-dependently until Day 28 after treatment, but showed an increase on Day 42, followed by a decrease on Day 70 after treatment. These data are strengthened by qualitative descriptions of lesions observed by histopathology. These results suggest that a high dose of 2-BP can decrease spermatogenesis by adversely affecting spermatogonia followed by depletion of spermatocytes, spermatids, and spermatozoa, with subsequent testicular atrophy. The atrophied testes may not regenerate completely. The number of Leydig cells may increase mildly with 10 weeks of recovery.

Histopathological evidence that spermatogonia are the target cells of 2-bromopropane

To confirm the target cell of 2-bromopropane within the testis, 1355 mg/kg of 2-bromopropane was subcutaneously injected to rats for 1-5 days and the numbers of spermatogonia and spermatocytes were examined 6 h after each last injection. The number of stage I spermatogonia decreased after the first 2-bromopropane injection and the number of spermatogonia at the other stages also decreased following repetitive injection. The number of these spermatogonia decreased further by the repetition of 2-bromopropane injection. In addition, the delay in mitotic division of type B spermatogonia was frequently observed after the fifth 2-bromopropane injection. The number of stage I pachytene spermatocytes also decreased slightly after the first 2-bromopropane injection, although it did not decrease further following repetitive injection. Therefore, we concluded that spermatogonia are the target cells of 2-bromopropane in rats.