Daily Archives: June 30, 2011

Thompson et al 2011: Cr-VI Mode of Action (MOA) Evidence

The drinking water community has been waiting patiently for results of toxicological studies that would help to clarify the mode of action (MOA) for chromium 6 (Cr-VI). The MOA is a key issue in assessing the risk presented by Cr-VI in drinking water.

The paper cited below appears to be the first of several to present results from this 90-day toxicology study. This paper discusses toxicokinetic, biochemical and pathological findings. Presumably future papers will discuss toxicogenomic findings. The authors state here:

“The 0.3 mg/L SDD [sodium dichromate dihydrate]  group in this study (0.1 mg/L Cr(VI)) is equivalent to the current federal drinking water standard for total chromium, and at this exposure no appreciable increases in tissue chromium levels or adverse effects were observed. Notably, the chromium concentrations in the duodenum at day 91 in the three highest treatment groups are estimated to approach or exceed 1 mM – a tissue dose that is clearly toxic in in vitro assays. These findings suggest that the doses that caused cancer in mice in the NTP study are associated with cytotoxicity in target tissues. Further, the increases in plasma GSH and GSSG levels observed at the highest concentrations in this study might reflect systemic oxidative stress and/or toxicity. In this regard, it was previously suggested that the bodyweight decreases observed in the NTP (2008) 2-year bioassay (similar to those in the present study) indicate that the highest SDD concentration may have exceeded the maximum tolerated dose (Stern, 2010).

Toxicology buffs can click here for the full paper (open source). The full citation and abstract are below.

 Thompson, C.M., D.M. Proctor, L.C. Haws, Hebert, S.D. Grimes, H.G. Shertzer, A.K. Kopec, J.G. Hixon, T.R. Zacharewski, and M.A. Harris. 2011. Investigation of the Mode of Action Underlying the Tumorigenic Response Induced in B6C3F1 Mice Exposed Orally to Hexavalent Chromium. Toxicol Sci. 2011 Jun 28.

Abstract (National Library of Medicine)

Chronic ingestion of high concentrations of hexavalent chromium [Cr(VI)] in drinking water induces intestinal tumors in mice. To investigate the mode of action (MOA) underlying these tumors, a 90-day drinking water study was conducted using similar exposure conditions as in a previous cancer bioassay, as well as lower (heretofore unexamined) drinking water concentrations.

Tissue samples were collected in mice exposed for 7 or 90 days, and subjected to histopathological, biochemical, toxicogenomic, and toxicokinetic analyses. Described herein are the results of toxicokinetic, biochemical and pathological findings. Following 90 days of exposure to 0.3-520 mg/L of sodium dichromate dihydrate (SDD), total chromium concentrations in the duodenum were significantly elevated at ≥ 14 mg/L. At these concentrations, significant decreases in the reduced-to-oxidized glutathione ratio (GSH/GSSG) were observed. Beginning at 60 mg/L, intestinal lesions were observed including villous cytoplasmic vacuolization. Atrophy, apoptosis, and crypt hyperplasia were evident at ≥ 170 mg/L. Protein carbonyls were elevated at concentrations ≥ 4 mg/L SDD, whereas oxidative DNA damage, as assessed by 8-hydroxydeoxyguanosine, was not increased in any treatment group. Significant decreases in the GSH/GSSG ratio and similar histopathological lesions as observed in the duodenum were also observed in the jejunum following 90 days of exposure. Cytokine levels (e.g. interleukin-1β) were generally depressed or unaltered at the termination of the study.

Overall, the data suggest that Cr(VI) in drinking water can induce oxidative stress, villous cytotoxicity, and crypt hyperplasia in the mouse intestine, and may underlie the MOA of intestinal carcinogenesis in mice.

San Diego Begins Wastewater Reclamation Pilot

The California coast is the ideal place to consider wastewater reclamation and San Diego joins Los Angeles in conducting a pilot demonstration study. The $11.8 million project has begun….

Click here for the news article.

Click here for another news article coverage.

Impellitteri et al 2011: Perchlorate in the Potomac River

A new article reports finding low levels of perchlorate in the Potomac River.  This river is the source of drinking water for Washington, DC.  Do you think that had any affect on the decision to monitor this particular river?  The abstract is below.

Perchlorate occurs naturally and as a manufactured compound. There is no mention in the abstract of the presumed source of the perchlorate detected.  Although the majority of levels found are below 1 ug/L, the abstract goes on to mention that :

“There was no evidence that any of the existing drinking water treatment technologies at the sampling sites were effective in removing perchlorate.” 

However, no treated water data is provided in the abstract.  If no treated water samples were taken, then perhaps there also is no evidence (evidence = data) that no perchlorate is being removed from drinking water at the sampling sites.  Hummm……

Imellitteri, C.A., J.P. Saxe, E.C. Schmitt, and K.R. Young. A survey on the temporal and spatial distribution of perchlorate in the Potomac RiverJ. Environ. Monit., 2011, Advance Article  DOI: 10.1039/C0EM00678E

USEPA-National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA. Impellitteri.christopher@epa.gov.

Abstract (National Library of Medicine)

Samples of river water and treated drinking water were obtained from eight sites along the Potomac River between western Maryland and Washington DC. Samples were collected each month from October 2007 to September 2008 and analyzed for perchlorate by ion chromatography/mass spectrometry. Data on anions were also collected for seven of the twelve months. Data were analyzed to identify spatial and temporal patterns for the occurrence of perchlorate in the Potomac.

Over the year of sampling, the largest monthly increase occurred from June to July, with levels then decreasing from July to September. Samples from the period between December and May had lower perchlorate concentrations, relative to the remainder of the study year. Spatially, higher levels of perchlorate were found at sites located in west-central Maryland, the eastern panhandle of West Virginia, and central northern Virginia, with levels decreasing slightly as the Potomac approaches Washington DC.

Within the sampling boundaries, river (untreated) water perchlorate concentrations ranged from 0.03 μg L(-1) to 7.63 μg L(-1), averaged 0.67 ± 0.97 μg L(-1) over the year-long period and had a median value of 0.37 μg L(-1). There was no evidence that any of the existing drinking water treatment technologies at the sampling sites were effective in removing perchlorate.

There were no correlations found between the presence of perchlorate and any of the anions or water quality parameters examined in the source water with the exception of a weak positive correlation with water temperature. Results from the summer (June-August) and fall (September-November) months sampled in this study were generally higher than from the winter and spring months (December-May).

All but one of the locations had annual average perchlorate levels below 1 μg L(-1); however, 7 of the 8 sites sampled had river water perchlorate detections over 1 μg L(-1) and 5 of the 8 sites had treated water detections over this level.

Click here for the abstract (free) and the paper (fee).

Having hiked the entire 183.5 mile Chesapeake and Ohio Canal as a kid, and attended the 4th of July fire works on the Washingtion Mall more times than I can remember, here’s a little something to celebrate the 4th.

“Operator Error” or Pump Failure in Dade City?

I find it curious that the reported water outage in Dade City, Florida was attributed to operator error.  Click here for the story. The pump apparently stopped working for some unknown reason…so wasn’t this outage cause by a pump failure? Why did the pump fail in the first place….that is the more important question. The incident would not have occurred if the pump had not failed. Additional clarification would be informative….