Article Review: Use of Field Test Kit for the Detection of Lead in Drinking Water in Philippines Post the Disaster Typhoon Yolanda (Haiyan) by K. Y. Liu et al.
Sofia Angela P. Federico
About 20 typhoons come to our country each year, damaging many properties and killing an average of 500 people annually. With our country being at the strike zone of the Pacific typhoon belt, it is always needed to reduce the risks of disasters that could be brought by this kind of natural hazard. Part of disaster risk reduction is assessing environmental risks with the potential to cause immediate harm to human lives, health, and the environment. After a typhoon, access to safe drinking-water is one of the most important public health concerns.
More than three years ago, typhoon Yolanda (international name “Haiyan”) wrecked huge havoc in the country especially in Tacloban, Leyte and its neighboring provinces and cities. According to official reports, about 5000 people died and 4 million were displaced. Many foreign countries provided humanitarian assistance including China. Aside from providing assistance in medical aid and epidemic prevention, a Chinese rescue team also took concern over heavy metal pollution that might be caused by the typhoon. Floods brought by typhoons may contain large amounts of heavy metals which could contaminate sources of drinking water. These heavy metals such as lead, when found excessive in drinking water, impose a great health threat to the people. Persons from the Chinese rescue team authored the article submitted to the journal Natural Hazards and Earth System Sciences concerning the lead contamination of tap water in Tacloban and Palo, Leyte.
The disease-prevention squad of the rescue team collected 27 samples of drinking water in Tacloban and Palo using commercial water recovery bags. The sampling method was not mentioned in the communication paper, or the exact places where they sampled the water, although the authors mentioned getting samples from tap water sources. Therefore, the authors did not provide an idea about how representative were the samples of the area. The lead content of these samples were measured in triplicate and by at least two inspectors using a commercial field test kit. The field method used was based on the reaction of lead ion with a reagent, dithizone.
Dithizone is a sulfur-containing organic compound. Dithizone easily forms complexes with many metals such as lead and mercury, making dithizone a good proxy indicator of these metals. Metal complexes are characterized by colors. When lead ions react completely with dithizone, bright-red internal-complex compound forms. If the color is not red, it means that dithizone, which contributes a yellow color, is in excess relative to any lead that may be present in the substance. Other reagents were also introduced to the test kit to reduce the interference of other ions that may cause inaccurate results. These reagents were not mentioned in the paper.
The authors mention a 1995 study by Berkowitz and his colleagues, in which a commercial lead test kit similar to what the authors used in Tacloban and Palo was claimed to have yielded results comparable with those obtained via more sophisticated laboratory analyses techniques such as X-ray diffraction (XRD) and inductively coupled plasma-mass spectrometry (ICPMS). They also mentioned a 2007 study by Jakariya and colleagues which claimed that the same commercial field test kit was able to determine correctly up to 91% the arsenic levels in samples that were analyzed first via atomic absorption spectroscopy (AAS). If indeed true, accurate but quick analysis of lead content in water especially after the passing of a disaster event would be much simpler, faster, and cheaper using the lead test kit.
The field test kits also contained four bottles of indicators. The indicators were successively dropped into the water, and the colors obtained were compared against a color calibration card three minutes after dropping. The water samples’ color may correspond to any of the six colors which indicates a particular concentration of lead: for example, if there is negliguble lead concentrations, the indicating color is yellow. Orange indicates a concentration of 0.5 mg per liter of the sample, pink indicates 2.0 mg per L of a sample, while red indicates a that there is very high amounts of lead in the sample (4.0 mg per L and above).
It was found out that the levels of lead in 18 tap water samples from 13 places, which comprised 67% of the total samples, showed colors between light orange and pink. This means that the tap water from these places have lead contents lying between 0.01 mg per liter and 2 mg per liter. These values exceeded the World Health Organization’s safety standard of 0.01 mg of lead per L. Of those 18 samples, four (4) showed colors corresponding to lead concentrations of 0.1 mg per liter up to 0.5 mg per liter. Nine (9) of the 18 samples had even higher concentration levels at more than 0.5 mg per liter.
The field test kit was simple, quick, and cheap to use for determining the lead content of the water samples. This would also make water testing immediately accessible especially in the field where a laboratory would most likely be unavailable in a post-typhoon setting. They also claimed that using field test kits such as the one they used in Leyte could be even deployed by relatively unskilled personnel since all that has to be done is to compare the color of the complex to the corresponding lead concentration indicated by a color card.
However, this method only provides semi-quantitative results, wherein it assigns or relates a qualitative characteristic (which in this case was color) to a certain or specific value such as the amount of lead. Thus, the best or the true values were not actually obtained. The authors also said that the color was hard to distinguish at lead concentrations that ranged from 0 mg per liter to 0.1 mg per liter. 28% of all of their samples had lead concentrations that were part of this problematic range. Color change was easier to recognize when the samples had higher lead concentrations such as 0.5 mg per liter. Color transition is seamless at lower lead concentrations, making it difficult to distinguish between two shades (and consequently, two distinct lead concentrations) at low lead levels. Field test kits are also still prone to giving false results because of manufacturing defect or other chemical interferences, such as other ions that might also react with lead and interfere with the coloring of the samples. These could lead residents to believe that the water in their area is safe to drink when it is actually not.
Crucially, the rescue team did not mention if the results of the field test were cross-checked by actual laboratory analyses. The team should have done this to confirm or falsify the validity of results and to make sure that the lead concentrations consistently corresponded with the color. They only vouched on previous literature for their kits’ result accuracy.
Creating simple devices for testing lead levels is a good subject for further research, as it is imperative for all stakeholders such as government and other concerned institutions to invent simple, cheap but accurate technologies for the testing of the safety of drinking water in the aftermath of calamities such as a typhoon, to which we are vulnerable as a country.
