Characterization of formaldehyde exposure resulting from the use of four professional hair straightening products.

An exposure simulation study was conducted to characterize potential formaldehyde exposures of salon workers and clients during keratin hair smoothing treatments. Four different hair treatment brands (Brazilian Blowout, Coppola, Global Keratin, and La Brasiliana) were applied to separate human hair wigs mounted on mannequin heads. Short-term (6-16 min) and long-term (41-371 min) personal and area samples (at distances of 0.5 to 3.0 m from the source) were collected during each treatment for the 1-day simulation. A total of 88 personal, area, and clearance samples were collected. Results were analyzed based on task sampling (blow-dry, flat-iron), treatment sampling (per hair product), and time-weighted averages (per hair treatment, four consecutive treatments). Real-time monitoring of tracer gas levels, for determining the air exchange rate, and formaldehyde levels were logged throughout the simulation. Bulk samples of each hair treatment were collected to identify and quantify formaldehyde and other chemical components that may degrade to formaldehyde under excessive heat. Mean airborne concentrations of formaldehyde ranged from 0.08-3.47 ppm during blow-dry and 0.08-1.05 ppm during flat-iron. During each treatment, the mean airborne concentrations ranged from 0.02-1.19 ppm throughout different zones of the salon. Estimated 8-hr time-weighted averages for one treatment per day ranged from 0.02 ppm for La Brasiliana to 0.08-0.16 ppm for Brazilian Blowout. For four treatments per day, means ranged from 0.04-0.05 ppm for La Brasiliana to 0.44-0.75 ppm for Brazilian Blowout. Using all four products in one day resulted in estimated 8-hr time-weighted averages ranging from 0.17-0.29 ppm. Results from bulk sampling reported formaldehyde concentrations of 11.5% in Brazilian Blowout, 8.3% in Global Keratin, 3% in Coppola, and 0% in La Brasiliana. Other products that degrade into formaldehyde were detected in Global Keratin, Coppola, and La Brasiliana. The results of this study show that professional hair smoothing treatments--even those labeled "formaldehyde-free"--have the potential to produce formaldehyde concentrations that meet or exceed current occupational exposure limits.

Exposure to chrysotile asbestos associated with unpacking and repacking boxes of automobile brake pads and shoes.

Industrial hygiene surveys and epidemiologic studies of auto mechanics have shown that these workers are not at an increased risk of asbestos-related disease; however, concerns continue to be raised regarding asbestos exposure from asbestos-containing brakes. Handling new asbestos-containing brake components has recently been suggested as a potential source of asbestos exposure. A simulation study involving the unpacking and repacking of 105 boxes of brakes (for vehicles ca. 1946-80), including 62 boxes of brake pads and 43 boxes of brake shoes, was conducted to examine how this activity might contribute to both short-term and 8-h time-weighted average exposures to asbestos. Breathing zone samples on the lapel of a volunteer worker (n = 80) and area samples at bystander (e.g., 1.5 m from worker) (n = 56), remote area (n = 26) and ambient (n = 10) locations collected during the unpacking and repacking of boxes of asbestos-containing brakes were analyzed by phase contrast microscopy and transmission electron microscopy. Exposure to airborne asbestos was characterized for a variety of parameters including the number of boxes handled, brake type (i.e. pads versus shoes) and the distance from the activity (i.e. worker, bystander and remote area). This study also evaluated the fiber size and morphology distribution according to the International Organization for Standardization analytical method for asbestos. It was observed that (i) airborne asbestos concentrations increased with the number of boxes unpacked and repacked, (ii) handling boxes of brake pads resulted in higher worker asbestos exposures compared to handling boxes of brake shoes, (iii) cleanup and clothes-handling tasks produced less airborne asbestos than handling boxes of brakes and (iv) fiber size and morphology analysis showed that while the majority of fibers were free (e.g. not associated with a cluster or matrix), <30% were respirable and even fewer were of the size range (>20 microm length) considered to pose the greatest risk of asbestos-related disease. It was found that average airborne chrysotile concentrations (30 min) ranged from 0.086 to 0.368 and 0.021 to 0.126 f cc(-1) for a worker unpacking and repacking 4-20 boxes of brake pads and 4-20 boxes of brake shoes, respectively. Additionally, average airborne asbestos exposures (30 min) at bystander locations ranged from 0.004 to 0.035 and 0.002 to 0.011 f cc(-1) when 4-20 boxes of brake pads and 4-20 boxes of brake shoes were handled, respectively. These data show that a worker handling a relatively large number of boxes of brakes over short periods of time will not be exposed to airborne asbestos in excess of its historical or current short-term occupational exposure limits.

Risk of gastrointestinal disease associated with exposure to pathogens in the sediments of the Lower Passaic River.

High levels of pathogenic microorganisms have been documented previously in waters of the Lower Passaic River in northern New Jersey. The purpose of this study was to characterize the microbial contamination of river sediments near combined sewer overflows (CSOs), a known source of pathogens. Concentrations of fecal coliform, total coliform, fecal Streptococcus, fecal Enterococcus, Pseudomonas aeruginosa, Staphylococcus aureus, Giardia lamblia, and Cryptosporidium parvum organisms were measured in 16 samples from three mudflat locations along the Lower Passaic River, as well as from an upstream location. Selected samples were also analyzed for antibiotic resistance. All of the samples contained high concentrations of total coliform, fecal coliform, fecal Streptococcus, and fecal Enterococcus organisms. Analysis of isolates of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli from several samples indicated that each strain was resistant to at least one antibiotic typically used in clinical settings. Eight of 16 samples contained Giardia, and one sample contained Cryptosporidium. With these sampling data, a quantitative microbial risk assessment was conducted to evaluate the probability of infection or illness resulting from incidental ingestion of contaminated sediments over a 1-year period. Three potential exposure scenarios were considered: visitor, recreator, and homeless person. Single-event risk was first evaluated for the three individual exposure scenarios; overall risk was then determined over a 1-year period using Monte Carlo techniques to characterize uncertainty. For fecal Streptococcus and Enterococcus, annualized risk estimates for gastrointestinal illness ranged from approximately 0.42 to 0.53 for recreators, 0.07 to 0.10 for visitors, and 0.62 to 0.72 for homeless individuals across the three sampling locations. Annualized risk of Giardia infection ranged from 0.14 to 0.64 for recreators, 0.01 to 0.1 for visitors, and 0.30 to 0.87 for homeless individuals, across all locations where detected. Cryptosporidium was detected at one location, and the corresponding annualized risk of infection was 0.32, 0.05, and 0.51 for recreators, visitors, and homeless individuals, respectively. This risk assessment suggests that pathogen-contaminated sediments near areas of CSO discharge in the Lower Passaic River could pose a health risk to individuals coming into contact with sediments in the mudflat areas.

DNA-protein cross-link formation in Burkitt lymphoma cells cultured with benzaldehyde and the sedative paraldehyde.

Exposure to aldehydes represents potential risks to human and animal health. Cyclic aldehydes such as benzaldehyde, 2-furaldehyde, and paraldehyde were found to induce formation of stable DNA-protein cross-links (DPXs) in cultured human lymphoma cells. A relationship between increased cytotoxicity and DPX formation was observed with each aldehyde. Paraldehyde is a sedative drug used predominately in treatment of ethanol withdrawal. Paraldehyde was the most potent cross-linking aldehyde studied, yet least cytotoxic. Although DPX formation by aliphatic aldehydes is well-known, this study confirms the potential for cyclic aldehydes to cause formation of DPXs in cultured cells at therapeutically relevant doses.

Evaluation of the physical hazards associated with two remedial alternatives at a Superfund site.

This study presents an evaluation of the risks due to the physical hazards associated with two remedial alternatives for a former chemical manufacturing facility in New Jersey. Both the on-site and off-site risk of work-related fatalities during remedy implementation and the risks of accident or accident-related fatalities during the off-site transport of site-related materials were evaluated. The two remedial alternatives evaluated were on-site containment and excavation with off-site incineration. The risk of at least one fatality due to a work-related accident was estimated for on-site activities associated with each remedial alternative, and for off-site incineration. The risks of at least one accident and of one accident-related fatality were calculated with accident and fatality data from the U.S. Department of Transportation. In addition, the risk of at least one accident that might potentially affect a natural resource (e.g., river, lake, or national park) was evaluated. This evaluation indicates that the risk of a work-related fatality is over an order of magnitude higher, and the risk of an accident or accident-related fatality is over three orders of magnitude higher, for the excavation/off-site incineration remedial alternative than for the on-site containment alternative. Overall, this study indicates that the physical hazards associated with excavation and off-site incineration are much greater than those associated with on-site containment for this site. Therefore, if a choice between the two remedial alternatives were to be made based solely on physical hazards and accident risk, the on-site containment alternative would be more protective of human health and the environment than the excavation/off-site incineration alternative.

DNA-protein cross-links as a biomarker of Cr(VI) exposure.

Comment on A. Zhitkovich et al. :Utilization of DNA-protein cross-links as a biomarker of chromium exposure. Environ Health Perspect 106(suppl 4):969-974 (1998).

An environmental hazard assessment of low-level dermal exposure to hexavalent chromium in solution among chromium-sensitized volunteers.

To evaluate the potential for elicitation of allergic contact dermatitis from contact with standing water in the environment, 26 persons known to be allergic to hexavalent chromium [Cr(VI)] were exposed to 25 to 29 mg/L Cr(VI) by immersion of one arm for 30 minutes per day on 3 consecutive days in a potassium dichromate bath. Sixteen of the 26 volunteers demonstrated either no or an equivocal response to the Cr(VI) challenge. Ten of the volunteers developed a few papules or vesicles (1 to approximately 15), mild redness, and pruritus on the Cr(VI)-challenged arm. Histopathological examination of the papules revealed spongiosis and perieccrine and perivascular inflammation. The responses were diagnosed as acute perieccrine reactions. It was concluded that exposure to similar concentrations of Cr(VI) in the environment does not pose an allergic contact dermatitis hazard, even to Cr-sensitized persons.

The prevalence of chromium allergy in the United States and its implications for setting soil cleanup: a cost-effectiveness case study.

Hexavalent chromium [Cr(VI)] elicits allergic contact dermatitis (ACD) among previously sensitized individuals, and some regulatory agencies have suggested the need for Cr(VI) soil standards that are protective of this health end point. To assess the cost effectiveness of implementing ACD-based standards, it is necessary to understand the prevalence of Cr(VI) sensitivity in the general population. More than 30 published studies from 1950 to 1997 were reviewed to determine the prevalence of Cr(VI) sensitivity. No random survey of the general United States (U.S.) population has been performed to date, but the prevalence of Cr(VI) sensitization among North American clinical cohorts (e.g., patients of dermatological clinics) was reported to be 1% in 1996. The prevalence of Cr(VI) sensitivity among the general U.S. population is estimated to be 0.08%. This estimate was calculated by dividing the current U.S. clinical prevalence estimate (1%) by the ratio of Cr(VI) sensitization in clinical vs general populations in The Netherlands (12). A retrospective cost/benefit analysis for sites in Jersey City, New Jersey, suggests that remediation of soils to protect against elicitation of ACD in sensitized individuals is not a cost-effective use of public health resources.

In vitro reduction kinetics of hexavalent chromium in human blood.

This study examines time- and concentration-dependent changes in distribution of hexavalent chromium [Cr(VI)] and total chromium [Cr-(TOT)] in reconstituted human blood following addition of potassium dichromate. Fresh human blood stabilized with EDTA was obtained from human volunteers soon after meal ingestion and at 2.5 h after a light meal (herein defined as "2.5-h fasted" conditions). Cr(VI) spiked into plasma under 2.5-h fasting conditions at 3.0-12.5 micrograms/L was stable for several hours, indicating a lack of appreciable reductive capacity in isolated plasma. Spiked plasma following a recent meal exhibited immediate but variable reduction of Cr(VI) up to 300 micrograms/L. When the spiked plasma was recombined with the red blood cell (RBC) fraction, rapid reduction occurred in both the plasma and the RBC fractions based on measurement of Cr(VI) and Cr(TOT). The data indicate that plasma reduction capacity is enhanced by a recent meal, but may be overwhelmed at Cr(VI) concentrations between 2000 and 10,000 micrograms/L. These data also suggest that the RBC fraction apparently has the capacity to reduce Cr(VI) at concentrations in blood up to 15,000 micrograms/L, and that the rate of Cr(VI) uptake into RBCs may not exceed the rate of intracellular reduction at these concentrations.

Preliminary assessment of PCB risks to human and ecological health in the lower Passaic River.

Concentrations of Aroclor mixtures and specific polychlorinated biphenyl (PCB) congeners were measured in surface sediments and aquatic biota (striped bass fillet, mummichog, and blue crab muscle and hepatopancreas) collected from the lower Passaic River. Several of the 47 surface sediment samples contained Aroclor concentrations that exceeded a National Oceanic and Atmospheric Administration (NOAA) benchmark level for "total PCBs" (22.7 micrograms/kg). Each of the 18 PCB congeners analyzed in aquatic biota was detected in one or more tissue samples, and numerous congeners were detected in every sample (IUPAC numbers 77, 105, 114, 118, 123, 126, 156, 157, 167, and 189). PCB congener concentrations were similar to those that have been reported in fish from other waterways that contain elevated levels of PCBs. Congener 118 was present at the highest concentration in almost all samples, and constituted 14-60% of the total PCB mass (sum of all congener masses) measured in any given tissue sample. In spite of the prevalence of PCB congeners in biota tissues (up to 1314 micrograms/kg total PCBs), Aroclors were not detected in bass or crab samples at a limit of detection of 33-55 micrograms/kg. This anomaly may be due to selective degradation of certain PCB congeners that are used to analytically recognize and quantitate Aroclors. Using the measured sediment concentrations, a food web model accurately predicted blue crab muscle concentrations of individual PCB congeners (typically within a factor of two) and was also fairly accurate for mummichog (typically within an order of magnitude). Concentrations in striped bass fillet were underestimated by factors of approximately 20-140. Increased cancer risk estimates associated with fish and crab consumption were obtained using four different methods. Using Aroclor tissue concentrations (one-half the limit of detection) and an Aroclor slope factor, total risks were 2.6 x 10(-6); using the "total PCB" measurements and an Aroclor slope factor, total risks were 1.9 x 10(-5); the "PCB-TEQ" method yielded total risks of 6.5 x 10(-4); and USEPA's recent suggested approach for evaluating "dioxin-like" and non-"dioxin-like" effects resulted in a total risk of 6.6 x 10(-4). This wide range in risk estimates indicates that it is critical to the risk management decision-making process that data requirements and risk assessment objectives be carefully evaluated early in the investigation process.

Urinary chromium as a biological marker of environmental exposure: what are the limitations?

Public concern has mounted recently about environmental exposures to chromium in soil, tap water, and ambient air. In response, agencies charged with protecting public health have attempted to study exposure by monitoring urinary chromium levels among potentially exposed populations. While urinary biomonitoring of occupationally exposed workers has been successfully used to assess high-level inhalation exposures in the workplace, evaluating low-level environmental exposures has been problematic. Due to these problems, before an extensive biological monitoring study is conducted of those exposed to low levels of environmental chromium, several issues must be resolved. First, exposures to chromium must occur at the same time as sampling, because the biological half-life of chromium in urine is very short (less than 2 days). Second, reduced bioavailability and bioaccessibility via the oral and dermal routes of exposure limit the capacity of urinary monitoring to measure environmental exposures (e.g., systemic dose is too small to be measured). Third, the dose of chromium must be sufficient such that it may be reliably measured above background levels in urine (range of 0.2 to 2 microg/liter) and above the analytical limit of detection (0.2 microg/liter). Fourth, the inter- and intrapersonal variability in background levels of urinary chromium is known to be significant and influenced by food and beverage intake, smoking, and exercise. Thus, the role of each factor must be carefully understood. Finally, it is imperative to have developed a complete understanding of the clinical significance of elevated urinary chromium levels before a study is performed, because higher than background levels, in and of themselves, are not indicative of a significant health concern. The route of exposure, valence of chromium to which people were exposed, exposure time, and duration must all be understood before the biological data can be implemented. We have conducted a total of nine human exposure studies over the past 3 years in an attempt to understand the kinetics of chromium and the impact on urinary, red blood cell (RBC), and plasma biomonitoring programs. The results of these studies are described here and our recommendations are offered for how to design and implement a urinary chromium biomonitoring study. In our view, given some evidence that the dose of hexavalent chromium [Cr(VI)] is sufficient to be measurable above background concentrations of total chromium [Cr(III) and Cr(VI)], duplicated measurements of chromium in plasma and RBCs are, in most cases, a more definitive gauge of environmental exposure than urinary biomonitoring.

Identification of an accurate soil suspension/dispersion modeling method for use in estimating health-based soil cleanup levels of hexavalent chromium in chromite ore processing residues.

The primary health concern associated with chromite ore processing residues (COPR) at sites in Hudson County, NJ, is the inhalation of Cr(VI) suspended from surface soils. Since health-based soil standards for Cr(VI) will be derived using the inhalation pathway, soil suspension modeling will be necessary to estimate site-specific, health-based soil cleanup levels (HBSCLs). The purpose of this study was to identify the most appropriate particulate emission and air dispersion models for estimating soil suspension at these sites based on their theoretical underpinnings, scientific acceptability, and past performance. The identified modeling approach, the AP-42 particulate emission model and the fugitive dust model (FDM), was used to calculate concentrations of airborne Cr(VI) and TSP at two COPR sites. These estimated concentrations were then compared to concentrations measured at each site. The TSP concentrations calculated using the AP-42/FDM soil suspension modeling approach were all within a factor of 3 of the measured concentrations. The majority of the estimated air concentrations were greater than the measured, indicating that the AP-42/FDM approach tends to overestimate on-site concentrations. The site-specific Cr(VI) HBSCLs for these two sites calculated using this conservative soil suspension modeling approach ranged from 190 to 420 mg/kg.

Background air concentrations of Cr(VI) in Hudson County, New Jersey: implications for setting health-based standards for Cr(VI) in soil.

An accurate measure of "background" airborne Cr(VI) concentrations will be necessary to derive site-specific health-based Cr(VI) soil concentrations at sites containing chromite ore processing residues (COPR) in Hudson County, NJ. To date, no such data have been collected in New Jersey. This paper describes an air sampling program designed to measure background concentrations of Cr(VI) in Hudson County and compare those concentrations with the air sampling results obtained previously at 30 COPR sites in Hudson County. Background airborne Cr(VI) concentrations ranged from 0.2 to 3.8 ng/m3 with an arithmetic mean of 1.2 ng/m3. Comparisons of the airborne Cr(VI) concentrations previously measured at 30 COPR sites indicated that more than two-thirds of the sites had mean airborne Cr(VI) concentrations that were not statistically significantly greater than background. Our findings suggest that, in general, vehicle disturbance is required for significant soil suspension to occur at these sites. Since airborne Cr(VI) concentrations at many of these sites are close to background, it is critical that background airborne Cr(VI) levels be considered when deriving health-based soil standards at the COPR sites.

Systemic uptake of chromium in human volunteers following dermal contact with hexavalent chromium (22 mg/L).

This study examined the systemic uptake of chromium in four human volunteers following three hours of contact with water containing hexavalent chromium [Cr(VI)] at a concentration of 22 mg/L. Volunteers were immersed below the shoulders in water at 91 +/- 2.5 degrees F. On the day prior to the experiment and for five days afterwards, samples of urine, plasma, and red blood cells (RBCs) were collected and analyzed for total chromium. Red blood cell chromium concentrations were used as a specific biomarker for systemic uptake of Cr(VI). Although total chromium concentrations in RBCs and plasma increased relative to historical background concentrations on the day of exposure, no sustained elevation of chromium concentrations was observed in RBCs or plasma of the volunteers tested. Since absorption of chromium in the hexavalent state would result in the irreversible binding of Cr(VI) to hemoglobin within the RBC (manifested as a sustained elevation of total chromium concentrations in the RBC), the pattern of blood uptake and urinary excretion observed was consistent with uptake and distribution of chromium in the trivalent state. Small increases were observed in the concentration of total chromium in urine within 48 h of exposure, indicating that some trivalent chromium [Cr(III)] may have penetrated the skin at a rate of about 3.3 x 10(-5) to 4.1 x 10(-4) micrograms/ cm2-h. In short, the data indicated that a 3-h contact with Cr(VI) at concentrations in water plausible for environmental exposure (e.g., swimming) was not expected to result in systemic uptake of measurable amounts of Cr(VI), although a small quantity of Cr(VI) may have penetrated the skin where it was subsequently reduced to Cr(III) prior to systemic uptake.

Ingestion of chromium(VI) in drinking water by human volunteers: absorption, distribution, and excretion of single and repeated doses.

This study examines the magnitude of hexavalent chromium [Cr(VI)] absorption, distribution, and excretion following oral exposure to 5 and 10 mg Cr(VI)/L in drinking water administered as a single bolus dose (0.5 L swallowed in 2 min) or for 3 d at a dosage of 1 L/d (3 doses of 0.33 L each day, at 6-h intervals). Adult male volunteers ingested deionized water containing various concentrations of potassium chromate, and samples of urine, plasma, and red blood cells (RBCs) were collected and analyzed for total chromium throughout the studies. In the bolus dose studies, a fairly consistent pattern of urinary chromium excretion was observed, with an average half life of about 39 h. However, 4-d total urinary chromium excretion and peak concentrations in urine and blood varied considerably among the 5 volunteers. Studies of repeated exposure to smaller volumes ingested at a more gradual rate (i.e., 0.33 L over 5-15 min) showed similar urinary chromium excretion patterns but generally lower chromium uptake/excretion. Given that sustained elevations in RBC chromium levels provide a specific indication of chromium absorption in the hexavalent state, these data suggest that virtually all (> 99.7%) of the ingested Cr(VI) at 5 and 10 mg Cr(VI)/L was reduced to Cr(III) before entering the blood-stream. The interindividual differences in total chromium uptake and excretion are plausibly explained by ingestion of appreciable doses on an empty stomach, which likely results in the formation of well-absorbed Cr(III) organic complexes in gastrointestinal tissues and possibly the blood. The lack of any clinical indications of toxicity in the volunteers and the patterns of blood uptake and urinary excretion of chromium are consistent with a predominant uptake of Cr(III) organic complexes [derived from Cr(VI)] that are excreted more slowly than inorganic forms of Cr(III). Therefore, it appears that the endogenous reducing agents within the upper gastrointestinal tract and the blood provide sufficient reducing potential to prevent any substantial systemic uptake of Cr(VI) following drinking-water exposures at 5-10 mg Cr(VI)/L. Based on these data, the chemical environment in the gastrointestinal tract and the blood is effective even under relative fasting conditions in reducing Cr(VI) to one or more forms of Cr(III).

Human ingestion of chromium (VI) in drinking water: pharmacokinetics following repeated exposure.

Regulatory agencies have established safe drinking water concentrations for hexavalent chromium [Cr(VI)] based in part on the presumed capability of human gastric juices to rapidly reduce Cr(VI) to nontoxic trivalent chromium [Cr(III)] prior to systemic absorption. This study examines dose-related pharmacokinetics in humans following repeated oral exposure to Cr(VI) in drinking water. In particular, we sought to examine whether plausible drinking water exposures to Cr(VI) caused a sustained increase in red blood cell chromium levels, a specific marker for systemic uptake of Cr(VI). Adult male volunteers ingested a liter (in three volumes of 333 ml, at approximate 6-hr intervals) of deionized water containing Cr(VI) concentrations ranging from 0.1 to 10.0 mg/liter. Samples of urine, plasma, and red blood cells were collected and analyzed for chromium. A dose-related increase in urinary chromium excretion was observed in all volunteers. Red blood cell and plasma chromium concentrations became elevated in certain individuals at the highest doses. The RBC chromium profiles suggest that the ingested Cr(VI) was reduced to Cr(III) before entering the bloodstream, since the chromium concentration in the RBCs dropped rapidly postexposure. These findings suggest that the human gastrointestinal tract has the capacity to reduce ingested Cr(VI) following ingestion of up to 1 liter of water containing 10.0 mg/liter of Cr(VI), which is consistent with USEPA's position that the Cr(VI) drinking water standard of 0.10 mg Cr(VI)/liter is below the reductive capacity of the stomach.

Absorption and elimination of trivalent and hexavalent chromium in humans following ingestion of a bolus dose in drinking water.

These studies investigate the magnitude and valence state of chromium absorbed following plausible drinking water exposures to chromium(VI). Four adult male volunteers ingested a single dose of 5 mg Cr (in 0.5 liters deionized water) in three choromium mixtures: (1) Cr(III) chloride (CrCl3), (2) potassium dichromate reduced with orange juice (cr(III)-OJ); and (3) potassium dichromate [Cr(VI)]. Blood and urine chromium levels were followed for 1-3 days prior to and up to 12 days after ingestion. The three mixtures showed quite different pharmacokinetic patterns. CrCl3 was poorly absorbed (estimated 0.13% bioavailability) and rapidly eliminated in urine (excretion half-life, approximately 10 hr), whereas Cr(III)-OJ was absorbed more efficiently (0.60% bioavailability) but more slowly (half-life, approximately 17 hr), and Cr(VI) had the highest bioavailability (6.9%) and the longest half-life (approximately 39 hr). All three chromium mixtures caused temporary elevations in red blood cell (RBC) and plasma chromium concentrations, but the magnitude and duration of elevation showed a clear trend (Cr(VI) > Cr(III)-OJ > CrCl3). The data suggest that nearly all the ingested Cr(VI) was reduced to Cr(III) before entering the bloodstream based on comparison to RBC and plasma chromium patterns in animals exposed to high doses of Cr(VI). These findings support our prior work which suggests that water-soluble organic complexes of Cr(III) formed during the reduction of Cr(VI) in vivo explain the patterns of blood uptake and urinary excretion in humans at drinking water concentrations of 10 mg/liter or less.

Urinary chromium concentrations in humans following ingestion of safe doses of hexavalent and trivalent chromium: implications for biomonitoring.

In this study, we evaluate the significance of increased urinary chromium concentrations as a marker of chromium exposure and potential health risk. Six human volunteers ingested trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)] at doses that are known to be safe but are much higher than typical dietary levels. The following dosing regimen was used: d 1-7, 200 micrograms/d chromium picolinate (a dietary supplement); d 8-10, Cr(VI) ingestion at the U.S. Environmental Protection Agency (EPA) reference dose (RfD) of 0.005 mg/kg/d; d 11-13, no dose; d 14-16, Cr(III) ingestion at the U.S. EPA RfD of 1.0 mg/ kg/d; and d 17-18, postdose. Urine voids were collected throughout the dosing periods and analyzed for chromium. Our findings are as follows: (1) ingestion of 200 micrograms/d of chromium picolinate yielded significantly elevated urine concentrations such that each participant routinely exceeded background, (2) ingestion of the Cr(VI) RfD (0.005 mg/kg/d) yielded individual mean urinary chromium levels (1.2-23 micrograms/L) and a pooled mean urinary chromium level (2.4 micrograms/L) that significantly exceeded background, and (3) ingestion of the Cr(III) RfD yielded no significant increase in urinary chromium concentrations, indicating that little, if any, absorption occurred. Our work identified three critical issues that need to be accounted for in any future studies that will use urinary chromium as a marker of exposure. First, a minimum urinary chromium concentration of approximately 2 micrograms/L should be used as a screening level to critically identify individuals who may have experienced elevated exposures to chromium. Second, if Cr(III) levels in soils are known to be less than 80,000 ppm and the Cr(III) is insoluble, urinary chromium concentrations are not an appropriate marker of exposure. Third, newer forms of chromium supplements that contain organic forms of Cr(III) must be considered potential confounders and their contribution to residential chromium uptake must be carefully evaluated.