Last Modified May 6th 2007
Chronic Arsenic Poisoning:
History, Study and Remediation

Introduction
Countries
Books
Conferences
References
MEASUREMENT
Site History
Remediation
Links
Harvard/MIT Faculty
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Online Articles
Chronic Health Effects
Pictures of Sufferers
Prof Wilson's Page


Magnitude of the problem  
 
     Arsenic contamination is becoming an increasingly common problem.  The laboratory  detectors are expensive and incapable of permitting the  large  numbers of measurements needed in a country such as Bangladesh,  where  there  are over 11,000,000 wells and where there is a need to continually verify that  the water is safe to drink.  At a conference in Dhaka  in December 1998,  the measurement capability of the country was estimated.  A simple calculation showed that it would take 300 years for all wells to be measured.! This was clearly inadequate, and  in 2002 there were still several million untested wells.  In 2005 this most of them have now been measured once the screening results are on the BAMWSP  website.   But there should be regular measurements of any well which is being used.    See also Feroze Ahmed's calculation of the cost. (reproduced below)   There are in general two types of measurement equipment:  Laboratory types with equipment costing $30,000 or so, which demand that water samples be brought to the laboratory (and for comparison split samples to several laboratories) and field measurements that are usually based on a change in color of some indicator.

Measurement reliability

    Traditionally a country has a bureau of weights and measured to ensure that all merchants give proper value for money and that a kilogram of rice in one place is thesame as a kilogram of rice in another.  There is regulation and frequent checking and intercalibration.    This should be, but is not,  the situation for arsenic.  As a result no one is sure whether any particlar remediation really works all the time, and a few supposedly clean wells can in fact be laden with arsenic with tragic results and loss of confidence. of the public in the government and NGOs.    An interlaboratory comparison of laboratory measurements of Arsenic was organized at the International Atomic Energy Agency in 2001 and is available in draft form.  Available also is a comment there on.  The results were not encouraging.  The expectation is that calibration of the field kits might well be worse.  In this webmaster's view, ensuring the reliability of the measurements should be a high priority particularly in Bangladesh.  Those trying to bring pure water to the peopleand those engaged in epidemiological analyses should not have to worry about the reliability of these measurements in addition to their other tasks.     However recent (May 2005) unpublished comparisons suggest that there is great improvement.   Only one out of 11 tested laboratories failed to measure consistently,  although 4 of the 11 were inaccurate.  However, although a laboratory reading systematially 30% low must correct its practices, this error is not imporatnt inn any decision to date.     

US EPA tests

Several arsenic test kits and sensors have been evaluated by the EPA Environmental Technology Verification program. Information on these technologies can be found at http://www.epa.gov/etv/verifications/vcenter1-21.html.

US EPA has a
review article on the subject.    They also produced the following table of test kits:

Table 1 Arsenic Test Kits and Sensors

Product Range of Arsenic Concentrations Detected (ppb) Accuracy (ETV Tests) Precision (ETV Tests) Total Test Time (Min)

ITS 481300 Quick™ Ultra Low II

0.2-30

Color Chart method: Bias ranged from -87% to 45%
Quick™ Arsenic Scan method: Bias ranged from -95% to 22%
Compu Scan method: Bias ranged from -92% to 161%

Color Chart method: RSD ranged from 0% to 84%
Quick™ Arsenic Scan method: RSD ranged from 2% to 78%
Compu Scan method: RSD ranged from 6% to 139%

12

ITS 481297 Quick™ Low-Range

2-80

Color Chart method: Bias ranged from -81% to 579%
Quick™ Arsenic Scan method: Bias ranged from -93% to 99%

Color Chart method: RSD ranged from 0% to 23%
Quick™ Arsenic Scan method: RSD ranged from 0% to 42%

12

Peters Engineering AS75 Arsenic Test Kit

2.5-60 (blue filter holder)
10-100 (grey filter holder)

PeCo test method: Bias ranged from 1% to 113%
AS 75 Tester method: Bias ranged from 1% to 310%

PeCo test method: RSD ranged from 0% to 41%
AS 75 Tester method: RSD ranged from 10% to 89%

No data

As-Top Water Test kit

10-500

Bias ranged from 2% to >9,900%

RSD ranged from 0% to 111%

30

Monitoring Technologies International PDV 6000

5-1000

Bias ranged from -74% to 31%

RSD ranged from 3% to 16%

Instrument calibration: 30 min.
Analysis: 5 min.

TraceDetect Nano-Band™ Explorer

1

Bias ranged from 1% to 499%

RSD ranged from 3% to 91%

< 1 min.


 


Matrix Interference Effects

Sodium chloride, iron, sulfate, and acidity can potentially interfere with arsenic measurements in water. However, in general, EPA found that the test kits and portable chemical sensors were not affected by the presence of sodium chloride, iron, sulfate, or acidity, and that measurements of arsenic were similar in samples that contained these potential interfering chemicals vs. samples that did not. EPA did find that high iron and/or hydrogen sulfide concentrations biased arsenic measurements by the PDV 6000 analyzer. Arsenic results in samples with high concentrations of iron and/or hydrogen sulfide were biased high.

 Standard Methods.

The following is from standard measurement methods for waste water "3500-As Arsenic (20th Edition)"  in 1997.   Standard measurements is now available on line/  

Methods are available to identify and determine total arsenic, arsenite, and arsenate. Unpolluted fresh water normally does not contain organic arsenic compounds, but may contain inorganic arsenic compounds in the form of arsenate and arsenite. The electrothermal atomic absorption spectrometric method (3113) is the method of choice in the absence of overwhelming interferences. The hydride generation-atomic absorption method (3114) is preferred when interferences are present that cannot be overcome by standard electrothermal techniques (e.g., matrix modifiers, background correction). The silver diethyldithiocarbamate method (3500-As B), in which arsine is generated by reaction with sodium borohydride in acidic solution, is applicable to the determination of total inorganic arsenic when interferences are absent and when the sample contains no methylarsenic compounds. This method also provides the advantage of being able to identify and quantify arsenate and arsenite separately by generating arsine at different pHs.  The inductively coupled plasma (ICP) method (3120) is useful at higher concentrations (greater than 50 µg/L) while the ICP/mass spectrometric method (3125) is applicable at lower concentrations if chloride does not interfere. When measuring arsenic species, document that speciation does not change over time. No universal preservative for speciation measurements has been identified.

An excellent up to date review of the methods was presented at the March 2006 American Chemical Society meeting by Dr Hussam of George Mason University, USA in March 2006.  When available ythe details will be posted on this site

Field Kits:

1)     Peters Engineering PeCo 75 and As 75 based on arsine generation
      (same thing, one with electronic color measurer, one visual)
2)     Envitop Ltd. As-Top Water arsenic test kit;  based on arsine generation
3)     Industrial Test Systems, Inc., QuickT test kit arsenic analysis systems; based on arsine generation. 
4)     NANO-BAND EXPLORER Portable Water Analyzer; using stripping anodic voltammetry.
    The above four were tested in 2002 by the USEPA as part of their Environmental Technology Verification Program
5)   QUICK kit.  This comes in several versions all under $200. 
6)     The Complete Arsenic Treatment Solution from Apyron Technologies
7)   
Merck Field Kit
The Merck kit is the most widely  used.  Tests were reported in the arsenic conference at DCH Dhaka in May 2000 and this was the only kit widely recommended.  But at that time it could only measure arsenic content above 100 microgram per liter (100 ppb) and even then is considered to be unreliable by many investigators.   In January 2002 some investigators trust it to 50 microgram per liter (100  ppb) but this does not seem to have been proven.     Arsenic Solutions are also working with the Finns to market their "Merck-type" field test kit, which seems to be improving all the time. The new version is slightly more expensive than the Merck kit and is claimed tol provide good results down to concentrations of arsenic in the water of 10 ppb, even when sulfide is present, as is common in Bangladesh. Arsenic Solutions also have a soil kit which Matt Simmons thinks is unique
8)    UNICEF field kit
No data available on this
9)    Hach Field kit
Some workers in the field claim that the Hach field kit is more sensitive and more reliable than the Merck kit.  The Columbia University scientists, in particular, have used it but recommend allowing 40 minutes for the measurements instead of the 20 minutes recommended by Hach.  This, Columbia University scientists claim, improves the reliability.   However the Hach kit is generally less  used because some field workers find it to be fragile.
10)    
CLEAN INDIA arsenic field kit.  This is made by CLEAN INDIA of New Delhi and is now being tested in the field in Bangaldesh and West Bengal.
11)      
Monitoring Technologies International, Pty. Ltd.  PDV 6000 Portable Analyzer (August 2003)   Verification Report  Verification Statement
12)        Equipment exists for X `ray fluorescence.  It is unclear whether this will work well for 10 ppb arsenic in the presence of 10 ppm of other chemicals
Roentec Ag Berlin  Principles Typical Trace  Article

Direct Reading Systems:

(1)  Biosensor measurement system from "Arsenic Solutions Inc"  (Matt Simmons)

This recent system involves the generation of light by modified E. coli in a solution.  The amount of light emitted allows quantitative measurements of the heavy metal content. It measures either TOTAL arsenic or arsenic III  content to about 1 ppb.  Matt Simmons believes  it can be cheap and made on the  Indian Subcontinent.  

(2)  A direct reading chemical device  -  the ARSENATOR .  

A combination chemical and electronic device has been devised by Dr. Walter Kosmos of the University of Graz inAustriaand called "The Arsenator".   This comes in two forms.  Alaboratory  instrument capable of accuate (3%) measurements down to1 microgramper litre  (1 ppb) and a field instrument capable of 10%measurementsdownto 5 microgramper litre  (5 ppb).  This deviceseems to be most promising and has the potential to meet the need.    However, at the 3rd International Arsenic Conference in Dhaka (May 2000) it was reported that the ARSENATOR is hard to use.  Batteries are unconventional (for Bangladesh)  and do not last.  Dust gets into the instrument.  It is fervently hoped that these difficulties can be overcome.   The capital cost of $1500 is high but it should be justifiable  -  if many measurements are taken.  Since one measurement takes 15 minutes, this could be done and is "only" a matter of organization.   The Arsenator was independently field tested in Myanmar by Dr Peter Swash, Imperial College, London and a team from the local UNICEF field office.    It seems that Wagtech International is now an arsenator sales representative. (Nick Price, Sales & Marketing Director, Wagtech International, United Kingdom  TEl:: +44 (0) 1635 872929; FAX: +44 (0) 1635 862898; mobile/cell  +44 (0) 7710 102182
(3)         Direct reading Equipment exists for X `ray fluorescence.  It is unclear whether this will work well for 10 ppb
arsenic in the presence of 10 ppm of other chemicals


Roentec Ag Berlin  Principles Typical Trace  Article

Biological Methods

    A new method using biological activity is being developed in Switzerland using simple bacterial biosensors  by Stocker et al. (see reference list). This will measure arsenite and arsenate in potable water.  Email: Barbara.Baumann@unil.ch.Prof. J. R. van der Meer, Dep. of Fundamental Microbiology, University of Lausanne, CH - 1015 Lausanne, Switzerland.
 

Measurement of Coliform Bacteria

    Everyone who has looked for microbiological contamination in water that has not been stored carefully has found gross contamination - water containers act as incubators in the house, especially when they are uncovered or do not have taps. After 12 hours, fecal coliforms can be more than 10,000/100ml, or even 'TNTC' (too numerous to count).  Dugwells if they are uncovered can have coliform bacteria also.    The primary way of avoiding such bacteria is to insist on santiary conditions:   Covered dugwells to keep out animals and pets and fecal matter.    But it is therefore very important to measure coliform bacterial contamination.   In principle this is easier than measuring low levels of arsenic and should be cheaper although it seems to cost about the same as testing for arsenic with a field kit.    An Indian made kit ( by Clean India ) cleanindia@sdalt.ernet.in. is available for measuring coliform bacteria and other contaminants (but not arsenic) at a cost of about $1 per measurement. This has been used for the last few years by Dhaka Community Hospital and has proven easy to use.    This kit maybe accessed directly at http://www.cleanindia.org/jaltarakit.htm or by e -mail to: temf@sdalt.ernet.in.

Laboratory measurement procedures:

Dr. Purnendu Dasgupta from Texas Tech University.  Dr. Dasguptais developing, researching and testing a field-deployable instrument for the measurement and speciationof arsenic in potable water.  To  see a copy of  Dr. Dasgupta's paper on his arsenic detection device, click here.

Neutron Activation is a standard for many arsenic measurements

Arsenic Analysis and Speciation by WCAS
 
   
Cost of Screening for As:

The arsenic content of water of tubewells within short distances varies widely in many palces. This is probably due to variation in the depth of tubewellsand geoenvironmental conditions of the strata of aquifers from which the tube wells abstract water. As a result, the levels of contamination in an area cannot be accurately predicted by testing of water of sample tubewells.Screening of all tubewells in the country is needed to identify the contaminated tubewell. Government of Bangladesh has decided to test arsenic content of water produced by all tubewells to identify the safe and unsafe tubewells. Bangladesh Arsenic Mitigation Water Supply Project and UNICEF have so far completed screening of all tubewells of 41 Upazillas and 5 Upazilas respectively.The estimated cost of field test kit only for the screening of estimated 7.5 million tube wells in the country is given below:

Number of tubewells : 7.5 Million ( Estimated)
Average number of tubewels can be tested by a Kit (100 test capacity) : 80
Number of Kits Required : 7 500 000/80 = 93 750
Average Cost of an Arsenic Test Kit : Tk 2 500 ( Assumed)
Cost of Test Kit : Tk. 2 500 x 93 750 = Tk. 234 375 000 @ Tk 234 Million or about $80 million.*

*The conversion rate for Tk/$ is approximately 30/1 .

The number of contaminated tubewells estimated on the basis of sample survey conducted by BGS and DPHE (2001) is 1.875 million which is 25% of the total estimated 7.5 million tubewells in Bangladesh. The present cost of this 1.875 million tubewells is Taka 8.44 billion. The significant deviations in intensity of contaminated tube wells by total screening from BGS/DPHE values justify the national screening program.
 
Monitoring of "safe" wells after screening:

The estimated 5.625 million manually operated deep and shallow tubewells still supplying water with arsenic below  national standard to 83 million people in the country are vulnerable to arsenic contamination in future.  No mathematical model can correctly predict the possible or probable time of contamination of these tubewells. In this situation, monitoring is the only way to know whether the tubewell is contaminated or not. The estimated cost of field kits for monitoring of the safe tubewells once per  year using a "field kit". is given below.   Laboratory measurements, which would be necessary for low levels, would be more expensive.

Monitoring Frequency : 1 Sample/year/Arsenic Safe (uncontaminated) Tubewell
Number of Uncontaminated Tubewell : 7 500 000 x 0.73 = 5 625 000
The Number of Kits Required with 80 tests per kit: 5 475 000/80 = 70 313
The cost of a Test Kit for 80 tests is Tk.2,500 or about $83 or $1 per test.
The total testing cost for Bangladesh is : Tk. 70 313 x 2 500 =Tk. 175 782 500 @ Tk. 176 Million or about $58 million
  
Since it is estimated that 87% tubewells are likely to be privately owned, testing of water for arsenic should be the responsibility of the owner. The testing of tube well water once in a year could be made mandatory.   Most experts recommend that a good test facility should be available locally, preferably at the lowest level of the Local Government body.   However this is not yet the case (2006).   


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