Embryotoxicity and fetotoxicity of orally administered hexavalent chromium in mice

Chromium levels in placental tissue and neural tube defects: Association and mechanistic study

Human exposure to chromium (Cr) is common but little is known about its adverse effects on pregnancy outcomes. This study aimed to explore the association between Cr exposure and the risk of neural tube defects (NTDs) and the underlying mechanisms of Cr-induced NTDs. 593 controls and 408 NTD cases with placentas were included in this study. Chromium trichloride (Cr(III)) and potassium dichromate (Cr(VI)) were intragastrically administered to pregnant mice and the number of NTDs was recorded. The odds ratio for total NTDs in the highest exposure group in placenta was 4.18 (95% confidence interval (CI), 1.97-8.84). The incidence of fetal NTDs in mice administered with Cr(III) showed a dose-response relationship. Cr(VI) didn't show teratogenicity of NTDs whereas increased the stillbirth rate. Prenatal exposure to Cr(III) increased levels of oxidative stress and apoptosis in fetal mice. RNA-sequencing results indicated significant enrichment of the MAPK pathway. RT-qPCR and Western blot analysis revealed that Cr(III) induced increased expression of p-JNK, p-P38, and Casp3. Toxicological effects can be partly antagonized by antioxidant supplementation. High chromium exposure was associated with increased human NTD risks. Excessive Cr(III) exposure can induce NTDs in fetal mice by increasing apoptosis through upgrading oxidative stress and then activating JNK/P38 MAPK signaling pathway.

A comprehensive review on human health effects of chromium: insights on induced toxicity

The growing use of heavy metals in most industrial activities has led to it being considered as the most important environmental pollutant that may cause harm and toxicity to animals and humans. Chromium has been found in the environment in different oxidation states such as Cr⁰, Cr(III), and Cr(VI) and is released from a variety of anthropogenic and natural activities. At among, trivalent and hexavalent chromium are the most stable forms. Considerably, Cr(VI) is frequently more toxic than Cr(III) because of its particular solubility and high mobility. Chronic exposure and bioaccumulation of chromium, as a heavy metal, can cause toxicity and numerous pathophysiological defects, including allergic reactions, anemia, burns, and sores especially in the stomach and small intestine, damage to sperm along with the male reproductive system, and affect various biological systems. Chromium pollution can have severe consequences for water and the soil environment. This article reviews the toxicological effects of Cr(VI) and Cr(III) and their mechanisms of toxicity and carcinogenicity.

Effects of embryonic exposure to chromium (VI) on blood parameters and liver microstructure of 1-day-old chickens

Hexavalent chromium (Cr(VI)) has carcinogenic, nephrotoxic, hepatotoxic, and neurotoxic effects. Exposure to Cr(VI) can also lead to hematological alterations and blood biochemical changes. The literature on Cr(VI) toxicity concerns mostly adult forms of vertebrates. In this study, an attempt was made to determine the effect on the developing chicken embryo of Cr(VI) in ovo administration. It was observed that chromium affected the hatchability of chicks in a dose-dependent manner. At a dose from 25 to 250 μg per egg, Cr(VI) resulted in a statistically significant reduction of hatchability. Chromium administrated at lower doses (1.56 and 2.5 μg per egg) caused a statistically insignificant increase of hatchability. However, chromium at a level of LD₅₀ (15.6 μg per egg) or 1/10 LD₅₀ (1.56 per egg) did not cause major changes in hematological parameters or plasma biochemical indices in newly hatched chicks. The same doses did not lead to any histopathological changes in the liver.

Oxidative Effects of Potassium Dichromate on Biochemical, Hematological Characteristics, and Hormonal Levels in Rabbit Doe (Oryctolagus cuniculus)

The present study was conducted to evaluate the toxicity induced by the increasing doses of potassium dichromate in rabbit doe. Twenty-eight adult does of 6 months of age were divided into four groups (A, B, C, and D; n = 7), with comparable average body weight (bw). Group A rabbits received only distilled water daily and served as a control, while groups B, C, and D received, respectively, 10 mg/kg bw, 20 mg/ kg bw, and 40 mg/kg bw of potassium dichromate via gavage for 28 days, after which animals were anesthetized with ether vapor and sacrificed. Blood samples were obtained via cardiac puncture and collected without anticoagulant for biochemical dosages and with anticoagulant (EDTA) for complete blood count. Follicle stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were dosed in serum and in homogenates of ovary with the help of AccuDiagTM ELISA kits from OMEGA DIAGNOSTICS LTD (Scotland, England) while respecting the immuno-enzymatic method. Activities of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and concentration of malondialdehyde (MDA) in liver, kidney, ovary and uterus were measured. Hematology revealed a significant (p < 0.05) decrease in mean values of hemoglobin and platelets while white blood cells and lymphocytes showed a significant (p < 0.05) increase in exposed groups. No significant (p > 0.05) difference was registered in monocytes, red blood cells, hematocrits, and plaquetocrits values with respect to the control. No matter the organ considered, no significant (p > 0.05) change was recorded in weight and volume. Nephrotoxicity analysis registered a significant (p < 0.05) increase in urea and creatinine, unlike renal tissue protein, which decreased significantly (p < 0.05). However, hepatotoxicity registered no significant (p > 0.05) variation in aspartate aminotransferase but total protein, alanine aminotransferase, and total cholesterol increased significantly (p < 0.05), while hepatic tissue protein revealed a significant (p < 0.05) decrease. Analysis on reproductive parameters showed a significant (p < 0.05) decrease in ovarian and uterine tissue proteins, as well as in follicle stimulating hormone, luteinizing hormone, and estradiol. Oxidative stress markers recorded no significant (p > 0.05) difference in glutathione reductase except in ovary where a significant (p < 0.05) decrease was seen when compared with the control, while catalase revealed a significant (p < 0.05) decrease, except in liver where there was no significant (p > 0.05) change. Superoxide dismutase and malondialdehyde recorded a significant (p < 0.05) decrease and increase respectively, with respect to the control. Results obtained from this study showed that the reduction process of chromium in tissues may cause the generation of reactive oxygen species, which are involved in hematoxic, nephrotoxic, hepatotoxic, and reproductive toxicity effects.

Occurrence of 44 elements in human cord blood and their association with growth indicators in newborns

There is growing concern about environmental pollution produced by elements, including "emerging" contaminants, such as rare earth elements (REE) and other trace elements (TE), which are extensively and increasingly employed in the manufacture of consumer electronics. Previous research has shown that prenatal exposure to some elements (mainly heavy metals) may be associated with decreased fetal growth and other adverse birth outcomes. Recent studies have also shown that environmental exposure to REE and TE may be related to adverse effects on human health. This cross-sectional study, which included nearly 92% of the births in 2016 in La Palma (Canary Islands, Spain; n = 471), aimed to evaluate the potential adverse health effects exerted by a wide range of elements on newborns. We quantified the levels of 44 elements (including 26 REE and TE) in their umbilical cord blood. Our results showed low or very low levels of most elements. We found an inverse association between antimony (Sb) and birth weight (Spearman's r = -0.106, p = 0.021). A similar trend was observed between nickel (Ni) and birth weight and between chromium (Cr) and birth length, although in this case the significance was borderline. Bismuth appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 3.30; 95% CI = 1.25-8.78; p = 0.017) and multivariate analyses (OR = 5.20; 95% CI = 1.29-20.91; p = 0.020). When assessing the effect of element mixtures, the sum of Cr, Ni, and Sb appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 2.41; 95% CI = 1.08-5.35; p = 0.031) and multivariate analyses (OR = 3.84; 95% CI = 1.42-10.39; p = 0.008). Our findings suggest that some inorganic elements-isolated or in mixture-are associated to a lower fetal growth. Additional research is needed to understand the role of inorganic pollutants on fetal development.

Prenatal chromium exposure and risk of preterm birth: a cohort study in Hubei, China

Few studies have investigated the association of environmental chromium exposure and preterm birth in general population. This study was designed to investigate whether maternal chromium exposure during pregnancy is associated with reduced gestational age or risk of preterm birth using the data from Healthy Baby Cohort study conducted in Hubei, China between 2012 and 2014 (n = 7290). Chromium concentrations in maternal urine samples collected at delivery were measured with inductively coupled plasma mass spectrometry. Tertiles of chromium concentrations was negatively associated with gestational age in multivariable linear regression analyses [β (95% CI): low = reference; middle = -0.67 days (-1.14, -0.20); high = -2.30 days (-2.93, -1.67); p trend <0.01]. Logistic regression analyses also indicated that higher maternal chromium [adjusted odds ratio (OR) (95% CI): 1.55(0.99, 2.42) for the medium tertile; 1.89(1.13, 3.18) for the highest tertile; p trend <0.01] was associated with increased risk of preterm birth. The associations appeared to be more pronounced in male infants (adjusted OR (95% CI): 2.54 (1.29, 4.95) for the medium tertile; 2.92 (1.37, 6.19) for the highest tertile; p trend <0.01). Our findings suggest maternal exposure to higher chromium levels during pregnancy may potentially increase the risk of delivering preterm infants, particularly for male infants.

Evaluation of Metal Ion Concentration in Hard Tissues of Teeth in Residents of Central Poland

Objectives. The aim of the study was an assessment of the content of trace elements in enamel and dentin of teeth extracted in patients residing in urban and agricultural areas of Poland. Methods. The study included 30 generally healthy patients with retained third molars. 65 samples of enamel and dentin from individuals living in urban areas and 85 samples of enamel and dentin from individuals living in agricultural areas were prepared. The content of manganese, lead, cadmium, and chromium in the studied enamel and dentin samples from retained teeth was determined by Graphite Furnace Atomic Absorption Spectrometry. In the process of statistical hypothesis testing, the level of significance was assumed at α = 0.05. Results. A comparative analysis of the data showed that enamel and dentin of inhabitants of industrialized areas contain significantly higher amounts of lead and cadmium than hard tissues of teeth in residents of agricultural areas and comparable amounts of manganese and chromium. Significance. It appears that hard tissues of retained teeth may constitute valuable material for assessment of long-term environmental exposure to metal ions. The study confirms that the risk of exposure to heavy metals depends on the place of residence and environmental pollution.

Developmental and interactive effects of arsenic and chromium to developing Ambystoma maculatum embryos: Toxicity, teratogenicity, and whole-body concentrations

Anthropogenic activity has contributed to elevated environmental concentrations of arsenic (As) and chromium (Cr). The spotted salamander, Ambystoma maculatum, may be useful for identifying developmental effects produced by exposure to these contaminants as adults breed and larvae develop in water that may contain As or Cr. Three sample sets among 700 developing larvae were exposed to a range of As, Cr, or 2.5:1 mixture of As:Cr concentrations, respectively. From these 700 larvae, samples containing approximately 24 larvae showed different patterns of whole-body As and Cr from individual and mixture exposure. Whole-body As concentrations were 20.27 and 45.4 µg/g dry weight for larvae exposed to 20 mg/L As and 25:10 mg/L As:Cr, respectively, while whole-body Cr concentrations were 24.8 and 22 µg/g dry weight for larvae exposed to 20 mg/L Cr and 25:10 As:Cr, respectively. Observed malformations included edema, tail kinking, facial deformities, and abnormal bending. Twelve-day lethal concentrations for As and Cr in Ambystoma maculatum larvae were 261.17 mg/L and 71.93 mg/L, respectively, while 12-d effective concentrations to induce malformations were 158.82 and 26.05 mg/L, giving teratogenic indices of 1.64 and 2.76 for individual metal exposure. Exposure to a mixture of As and Cr resulted in a response addition and yielded lower lethal and effective concentration values with a teratogenic index of 2.78, indicating that these contaminants are developmentally toxic at lower concentrations when exposed as a mixture. Data demonstrate that As and Cr affect development of amphibian larvae, and that Ambystoma maculatum may be a useful indicator of environmental toxicity for these metals.

Toxic and genotoxic effects of hexavalent chromium in environment and its bioremediation strategies

Chromium is one of the major inorganic environmental pollutants, which is added in the environment through various natural and anthropogenic activities and exists mainly in two forms: Cr(III) and Cr(VI). Cr(VI) is considered to be more toxic than Cr(III) due to its high solubility and mobility. It is a well-reported occupational carcinogen associated with lung, nasal, and sinus cancers. Thus, this review article provides the detailed information on the occurrence, sources of chromium contamination in the environment and their toxicological effects in human, animal, plants as well as in microorganisms, and bioremediation strategies to minimize the toxic effects.

Evidence for bystander signalling between human trophoblast cells and human embryonic stem cells

Maternal exposure during pregnancy to toxins can occasionally lead to miscarriage and malformation. It is currently thought that toxins pass through the placental barrier, albeit bi-layered in the first trimester, and damage the fetus directly, albeit at low concentration. Here we examined the responses of human embryonic stem (hES) cells in tissue culture to two metals at low concentration. We compared direct exposures with indirect exposures across a bi-layered model of the placenta cell barrier. Direct exposure caused increased DNA damage without apoptosis or a loss of cell number but with some evidence of altered differentiation. Indirect exposure caused increased DNA damage and apoptosis but without loss of pluripotency. This was not caused by metal ions passing through the barrier. Instead the hES cells responded to signalling molecules (including TNF-α) secreted by the barrier cells. This mechanism was dependent on connexin 43 mediated intercellular ‘bystander signalling’ both within and between the trophoblast barrier and the hES colonies. These results highlight key differences between direct and indirect exposure of hES cells across a trophoblast barrier to metal toxins. It offers a theoretical possibility that an indirectly mediated toxicity of hES cells might have biological relevance to fetal development.

Persistent hexavalent chromium exposure impaired the pubertal development and ovarian histoarchitecture in wistar rat offspring

Hexavalent chromium (CrVI) is a highly toxic metal and a major environmental pollutant. Several studies indicate that CrVI exposure adversely affects reproductive function. We reported that maternal Cr exposure resulted in Cr accumulation in the reproductive organs of female offsprings. CrVI can cross the placental barrier and also can be passed through breastfeeding. The present investigation aimed to determine the persistent (in utero through puberal period) CrVI exposure-induced toxic effects on the reproductive functions of mother and the offspring. Induction of oxidative stress is one of the plausible mechanisms behind Cr-induced cellular deteriorations. Mother rats exposed to CrVI showed reduced reproductive outcome, while the offsprings showed higher accumulation of Cr in ovary, altered steroid, and peptide hormones. Specific activities of antioxidant enzymes were decreased and associated with increased levels of H2 O2 , and lipid peroxidation. CrVI exposure also damaged the ovarian histoarchitecture in various age groups studied. CrVI exposure also delayed the sexual maturation. Results from the present investigation suggest that CrVI exposure from in utero through puberal period significantly damaged the pubertal development through altered antioxidants, anemia, and altered hormone levels. These changes were associated with damaged ovarian histoarchitecture and extended estrous cycle in developing Wistar rats.

An exploratory study of ambient air toxics exposure in pregnancy and the risk of neuroblastoma in offspring

Little is known about the etiology of neuroblastoma, the most common cancer in infancy. In this study, we examined maternal exposure to ambient air toxics in pregnancy in relation to neuroblastoma in the child. We ascertained all cases of neuroblastoma listed in the California Cancer Registry 1990-2007 that could be linked to a California birth certificate, and controls were selected at random from California birth records. Average air toxics exposures during pregnancy were determined based upon measures from community-based air pollution monitors. The study included 75 cases and 14,602 controls who lived with 5 km of an air pollution monitor, and we additionally examined results for those living within a smaller radius around the monitor (2.5 km). Logistic regression was used to determine the risk of neuroblastoma with one interquartile range increase in air toxic exposure. Neuroblastoma risk was increased with higher maternal exposure to carbon tetrachloride (OR=2.65, 95%CI 1.07, 6.53) and polycyclic aromatic hydrocarbons (OR=1.39, 95%CI 1.05, 1.84), particularly indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene. Hexavalent chromium was associated with neuroblastoma at the 5 km distance (OR=1.32, 95%CI 1.00, 1.74) but not at the 2.5 km distance. This is one of the first studies to report associations between neuroblastoma and these air toxics.

Toxic effects of chromium (VI) by maternal ingestion on liver function of female rats and their suckling pups

Potassium dichromate (K(2)Cr(2)O(7)) is an environmental contaminant widely recognized as a carcinogen, mutagen, and teratogen toward humans and animals. This study investigated the effects of K(2)Cr(2)O(7) on the hepatic function of pregnant and lactating rats and their suckling pups. Experiments were carried out on female Wistar rats given 700 ppm of K(2)Cr(2)O(7) in their drinking water from the 14th day of pregnancy until day 14 after delivery. Hepatotoxicity was objectified by the significant increase in liver malondialdehyde content and a significant accumulation of chromium in this soft tissue. Moreover, exposure to K(2)Cr(2)O(7) induced a decrease of glutathione, nonprotein thiols, and vitamin C in the liver of mothers and their suckling pups. Alteration of the antioxidant system in the treated group was confirmed by the significant decline of antioxidant enzyme activities such as catalase, glutathione peroxidase, while liver superoxide dismutase activity increased in mothers and decreased in their offspring. It was found that K(2)Cr(2)O(7) induced liver damages as evidenced by the elevation of plasma aminotransferases, lactate dehydrogenase activities, and bilirubin levels. Impairment of the hepatic function corresponded histologically. Our investigation revealed hemorrhage, leukocytes infiltration cells, and necrosis, which were more pronounced in the hepatocytes of mothers than in those of their suckling pups.

Oxidative stress induced by chromium (VI) in bone of suckling rats

Exposure to hexavalent chromium Cr(VI) compounds is of concern in many Cr-related industries and their surrounding environments. K2Cr2O7 is widely recognized as an animal and human carcinogen, mutagen, and teratogen. The present study investigated the bone maturity of suckling rats whose mothers were treated with K2Cr2O7. Experiments were carried out on female Wistar rats given 700 ppm of K2Cr2O7 in their drinking water from the 14th day of pregnancy until day 14 after delivery. Exposing dams to K2Cr2O7 caused disorders in the bone of their progeny. As corollary to this, malondialdehyde levels increased, while glutathione, a non-protein thiol and vitamin C decreased. Alteration of the antioxidant system in the treated group was also confirmed by the significant decline of superoxide dismutase, catalase, and glutathione peroxidase activities. Furthermore, K2Cr2O7 induced changes in bone mineralization, especially calcium and phosphorus levels, which decreased. Whereas, in plasma and urine, they increased and decreased inversely. These results suggest that K2Cr2O7 accelerated bone resorption activity. In fact, in treated pups, total tartrate-resistant acid phosphatase, which reflected bone resorption, was enhanced while total alkaline phosphatase, which reflected bone formation, was reduced. The impairment of bone function was corresponded histologically.

Nephrotoxicity induced by chromium (VI) in adult rats and their progeny

To assess kidney damages in pregnant and lactating rats and in their suckling pups, Wistar female rats were given, through drinking water, 700 parts per million (ppm) of K2Cr2O7 from the 14th day of pregnancy until day 14 after delivery. Toxicity was objectified by a significant increase in malondialdehyde (MDA), glutathione (GSH) and nitric oxide (NO) levels in kidney of chromium-treated mothers and their suckling pups. Moreover, lactate dehydrogenase (LDH) was increased in kidney and decreased in plasma of K2Cr2O7-treated rats. Activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were increased in dams and decreased in their pups. Interestingly, these biochemical modifications were accompanied by higher plasma and lower urinary levels of creatinine, a specific indicator of glomerular function, and of urea than those of controls. Significant increase in creatinine clearance was also found in treated mothers and in their progeny. Histological studies showed an infiltration of mononuclear cells, necrosis and vascular congestion in kidney of pups and dams. Based on the present findings, K2Cr2O7 administrated to female rats during late pregnancy and early postnatal periods provoked kidney damages in dams and their offspring.

Protective effects of Selenium (Se) on Chromium (VI) induced nephrotoxicity in adult rats

Chromium is a toxic metal implicated in human diseases. This study was focused on investigating the possible protective effect of Se against K(2)Cr(2)O(7). Female Wistar rats, used in this study, were divided into four groups of six animals each: group I served as control which received standard diet; group II received orally only K(2)Cr(2)O(7) (700 ppm equivalent to 67 mg/kgbw); group III received both K(2)Cr(2)O(7) and Se (0.5 mg/kg of diet); group IV received Se (0.5mg Na(2)SeO(3)/kg of diet). The exposure of rats to K(2)Cr(2)O(7) for 21 days provoked renal damages with a significant increase in kidney malondialdehyde, superoxide dismutase, plasma creatinine, and uric acid levels, while catalase, glutathione peroxidase, non-protein thiol, Metallothionein and plasma urea levels decreased. Coadministration of Se in the diet of chromium-treated group improved malondialdehyde, renal biomarkers levels and antioxidant enzyme activities. Kidney histological studies confirmed biochemical parameters and the beneficial role of selenium.

Developmental toxicity, uptake and distribution of sodium chromate assayed by frog embryo teratogenesis assay-Xenopus(FETAX)

The embryotoxicity and teratogenicity of Cr(VI) on the survival and morphology of the anuran Xenopus laevis have been assessed by frog embryo teratogenesis assay-Xenopus (FETAX). The lethal median (LC(50)) and teratogenic median (TC(50)) concentration values of Cr(VI) were 890 microM and 260 microM, respectively. The calculated teratogenic index (TI) value was 3.42, suggesting that hexavalent chromium has a teratogenic potential. Malformations of embryos included lifting of the body, coiling of the tail and body oedema. Furthermore, the chromium salt caused significant growth retardation at 25 microM exposure concentrations. The use of radiolabelled (51)Cr(VI) allowed the determination of the time course uptake of Cr in Xenopus exposed to concentrations ranging from 0.025 to 500 microM. The evaluation of its distribution into the body (head-abdomen-tail) was evaluated at different exposure times. Chromium is taken up at 24 h by Xenopus embryos for all concentrations tested. At 48 h post fertilization (stage of larva) the amount of Cr accumulated by the two-day-old larva ranged from 0.42 to 580 pg mg(-1) wet weight at 0.025 and 500 microM respectively. These amounts were lower than those at 24 h (2.77 to 11016 pg mg(-1) wet weight embryo) reaching values of the same order of magnitude at 120 h (five-days-old larva). Since at 48 h Xenopus development leads to a swimming embryo, the observed uptake at 24 h could be the result of the binding of Cr to jelly coat compounds surrounding the embryo body as confirmed by gel filtration experiments on (51)Cr-jelly coat. The interaction of Cr with jelly coat is in agreement with the role of jelly coat in protecting the embryo against pathogen and chemical toxins to ensure fertilization. This work further supports the hypothesis that Cr contamination of surface waters could contribute to explain the reported worldwide depletion of frog population.

Exposure of pregnant mice to chromium picolinate results in skeletal defects in their offspring

BACKGROUND

Chromium(III) picolinate, [Cr(pic)(3)], is a widely marketed dietary supplement. However, Cr(pic)(3) has been associated with oxidative damage to DNA in rats and mutations and DNA fragmentation in cell cultures. In isolated case reports, Cr(pic)(3) supplementation has been said to cause adverse effects, such as anemia, renal failure, liver dysfunction, and neuronal impairment. To date, no studies have been published regarding the safety of chromium picolinate supplementation to a developing fetus, although Cr(pic)(3) has been recommended for pregnant women who are diagnosed with gestational diabetes.

METHODS

From gestation days (GD) 6-17, pregnant CD-1 mice were fed diets containing either 200 mg/kg Cr(pic)(3), 200 mg/kg CrCl(3), 174 mg/kg picolinic acid, or the diet only to determine if Cr(pic)(3), CrCl(3), or picolinic acid could cause developmental toxicity. Dams were sacrificed on GD 17, and their litters were examined for adverse effects.

RESULTS

The incidence of bifurcated cervical arches was significantly increased in fetuses from the Cr(pic)(3) group as compared to the diet-only group. Fetuses in the picolinic acid-treated group had an incidence double that of the control group; however, this increase was not statistically significant. Fetuses in the CrCl(3) group did not differ from the controls in any variable examined. No maternal toxicity was observed in any of the treatment groups.

CONCLUSIONS

High maternal oral exposures to chromium picolinate can cause morphological defects in developing offspring of mice.

Semen quality of industrial workers occupationally exposed to chromium

A total of sixty-one subjects occupationally exposed to chromium in an industry which manufactures chromium sulphate and fifteen control subjects from a nearby industry which does not manufacture any chromium related compounds were studied. The history of each subject was recorded on pre-designed form through interview and a routine medical examination was carried out. Blood samples (5-6 ml) were collected for the estimation of chromium and semen samples were collected for semen analysis and the determination of copper and zinc levels in the seminal plasma. Clinical examination revealed nasal perforation in 10 subjects (out of 61) in the exposed group as compared to none in the control group. A significantly higher level of chromium was observed in the blood of the exposed workers as compared to the control. The concentration of zinc in seminal plasma was lower while the level of copper was higher in the exposed group as compared to the control. However, these changes were not statistically significant. Statistically significant higher numbers of morphologically abnormal sperms were noticed in the exposed group with respect to the control. Further analysis of the data indicated that about 53% of the exposed subjects showed less than 30% normal forms as compared to 10% in control subjects. However, no significant alterations in semen volume, liquefaction time, mean pH value, sperm viability, concentration or motility, were noticed between chromium exposed and unexposed workers. The data also indicates that exposure to chromium has some effect on human sperm as a significant positive correlation (r=0.301) was observed between percentages of abnormal sperm morphology and blood chromium levels (p=0.016) after pooling all the data of the control and exposure groups.

Agency for Toxic Substances and Disease Registry's 1997 priority list of hazardous substances. Latent effects--carcinogenesis, neurotoxicology, and developmental deficits in humans and animals

In support of Superfund re-authorization legislation, the Division of Toxicology of the Agency for Toxic Substances and Disease Registry (ATSDR) prepared a chemical-specific consultation document for Congress that identified those chemicals with carcinogenic, neurological, or developmental adverse effects having a latency period longer than 6 years. The review was limited to the top 50 substances listed on ATSDR's 1997 Priority List of Hazardous Substances (Priority List). Among the top 50 chemicals, a review of the technical literature indicated that 38 (76%) were classified as "reasonably anticipated," "possibly," or "probably" capable of causing cancer in humans, based either on human and animal data. Eight chemicals (16%) had well-established cancer latency periods in humans of 6 years or more following exposure. Three substances (6%)--arsenic, creosote, and benzidine--had data indicating latency periods longer than 6 years. The technical literature review likewise confirmed the potential for neurological and developmental effects with a latency of 6 years. Twenty-seven (54%) of the top 50 substances caused acute and/or chronic neurotoxic effects; a number of these also caused neurological effects that persisted beyond 6 years (or the equivalent in animal studies) such as: behavioral problems, neurological deficiencies, reduced psychomotor development, cognitive deficiencies, and reduced IQ. Twenty-eight substances (56%) caused adverse developmental effects in offspring of exposed individuals or animals including increased fetal and infant mortality, decreased birth weights and litter sizes, and growth delays. Latency periods for related chemicals are expected to be similar due to structural and toxicological similarities.

Chromium

Chromium occurs primarily in the trivalent state (III), which is the most stable form, or in the hexavalent state (VI), which is a strong oxidizing agent. Elemental chromium (0) does not occur naturally on earth. Trivalent chromium (III) is an essential trace metal necessary for the formation of glucose tolerance factor and for the metabolism of insulin. Commercial applications of chromium compounds include tanning (III), corrosion inhibition, plating, glassware-cleaning solutions, wood preservatives (VI), manufacture of safety matches, metal finishing (VI), and the production of pigments (III, VI). Hexavalent chromium (VI) contaminated local soil when chromium waste slag was part of the fill material present in residential, public, and industrial areas. In some urban areas, about two-thirds of the chromium in air results from the emission of hexavalent chromium from fossil fuel combustion and steel production. The remaining chromium in air is the trivalent form. The residence time of chromium in air is < 10 days, depending on the particle size. Trivalent compounds generally have low toxicity and the gastrointestinal tract poorly absorbs these compounds. Hexavalent chromium is a skin and mucous membrane irritant and some of these hexavalent compounds are strong corrosive agents. Hexavalent chromium compounds also produce an allergic contact dermatitis characterized by eczema. Sensitivity to trivalent compounds is much less frequent, but some workers may react to high concentrations of these compounds. Hexavalent chromium is recognized by the International Agency for Research on Cancer and by the US Toxicology Program as a pulmonary carcinogen. The increased risk of lung cancer occurs primarily in workers exposed to hexavalent chromium dust during the refining of chromite ore and the production of chromate pigments. Although individual studies suggest the possibility of an excess incidence of cancer at sites outside the lung, the results from these studies are inconsistent.

Embryo and fetotoxicity of hexavalent chromium: a long-term study

Ingestion of chromium(VI) (250, 500 or 750 ppm as potassium dichromate, K2Cr2O7) through drinking water by female rats for 3 months prior to gestation was toxic to embryo and fetus. There was a significant reduction in number of implantations and number of fetuses and an increase in number of resorptions and pre-implantation and post-implantation losses. No significant visceral abnormality was found. The increase in the number of subdermal hemorrhagic patches on the thorax and abdomen was significant. Skeletal abnormality in the form of reduced ossification in parietal, interparietal and caudal bones was observed in fetuses. Chromium levels in the blood of mothers, placenta and fetuses showed a significant increase. Duration of the estrous cycle was also increased significantly. The study revealed that long-term chromium exposure in rats did not cause embryo and fetotoxicity in a duration-dependent manner compared to short-term treatment as observed earlier. A possible explanation could be that, in the 90-day study, the female rats did not mate for three estrous cycles, thus giving time for clearance of a sizable amount of chromium from their bodies.

Ovarian dysfunction in mice following chromium (VI) exposure

Chromium (VI) was given through drinking water in two sets of adult Swiss albino female mice in three doses; 250 ppm, 500 ppm and 750 ppm for 20 days in set 1 and 0.05 ppm, 0.5 ppm and 5.0 ppm in set II for 90 days. At the termination of the treatment, the animals of both the sets were euthanized for histopathology, follicle counting, counting of the superovulated ova, duration of estrus cycle and for ultrastructural studies. Ovaries of the highest dose group (750 ppm) showed large numbers of atretic follicles and congestion in stromal tissue compared to the rest of the treated groups. Also, there was a dose-dependent reduction in the number of follicles at different stages of their maturation. The number of ova recovered from superovulated chromium (VI)-treated animals showed significant decreases in the 500 and 750 ppm dosed groups compared to lower dosed (250 ppm) and control groups. The duration of estrus cycle increased in highest dosed (750 ppm) group. A dose-dependent increase in blood chromium level was also seen in treated mice. Ultrastructural observations revealed disintegrated cell membranes of two layered follicular cells and altered villiform mitochondria in thecal cells of 5 ppm dosed group. From the study it was concluded that ovarian physiology and rate of ovulation might be altered if females are exposed to sufficiently high chromium through oral route.

Embryotoxicity of orally administered chromium in mice: exposure during the period of organogenesis

Administration of chromium (VI)(250, 500 and 750 ppm as potassium dichromate) via drinking water during organogenesis (days 6-14 of gestation) in mice revealed embryo- and fetotoxic effects. Reduced fetal weight, retarded fetal development, number of fetuses (live and dead) per mother and high incidences of dead fetuses and resorptions in treated mothers in the highest dosed group were evident. No significant gross structural abnormalities were observed in any of the fetuses of chromium (VI)-treated mothers. Significant incidences of reduced ossification were found in the highest dosed group. Chromium levels were increased in a dose-dependent manner in maternal blood, placenta and fetuses. The present study suggests a risk to the developing embryo if the mother is exposed to a sufficiently high concentration of chromium (VI) through drinking water during the period of organogenesis.

Chromium-induced production of reactive oxygen species, DNA single-strand breaks, nitric oxide production, and lactate dehydrogenase leakage in J774A.1 cell cultures

The involvement of oxidative stress in the toxicity of chromium (VI) and chromium (III) has been proposed. We have therefore examined the effects of these cations on the production of superoxide anion, nitric oxide (NO), and DNA single strand breaks (SSB) in J774A.1 macrophage cells in culture as well as the effects on lactate dehydrogenase (LDH) leakage and cell viability. Following a 48 hour incubation, over twofold increases in superoxide anion and NO production were observed at concentrations of approximately 0.30 and 50 microM for Cr (VI) and Cr (III), respectively. The patterns of cell viability and LDH leakage paralleled superoxide anion and NO production for Cr (VI) and Cr (III). A 50% decrease in viability was observed at approximately the concentrations that produced a twofold increase in superoxide and NO production. Concentration-dependent increases in DNA-SSB were observed after incubation with Cr (III) with maximum increases occurring at a concentration of approximately 60 microM. Cr (VI) had no effect on the incidence of DNA-SSB at any of the tested concentrations. The results indicate that Cr (VI) and Cr (III) are toxic to the J774A.1 cell line, and the toxicity may be due at least in part to an oxidative stress induced by the production of reactive oxygen species.