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Table 2. Common Food Contaminants and Related Health Hazards


Health hazard

Formalin:Formalin is a 37% formaldehyde aqueous solution.

WHO average         daily exposure

Food                           9.4 mg/d

Inhalation                   1.0 mg/d

Water                         0.15 mg/d

Total:                        10.55 mg/d

Naturally Occurring Formaldehyde in Food

Food type        Formaldehyde level (ppm)

Cow’s milk                <3.3

Shrimp                     1-2.4

Beef                         4.6

Poultry                     2.5-4.2

Potato                     10.0-13.5

Cucumber                 2.3-3.0

Cabbage                   3.5-5.2

Exposure to formaldehyde is possible in two ways. One is through breathing air with formaldehyde and other is the absorption of formaldehyde through the skin. The harmful effects of such exposure can range from mild to life-threatening ones.

If the level of formaldehyde is between 0.1 to 5 ppm, irritation of the eyes, tears, skin and respiratory tract irritation can be caused. If the formaldehyde level is between 5 to 20 ppm, it may cause breathing trouble, cough and burning of the eyes and skin. In case of high formaldehyde levels, i.e. 20 to 100 ppm, severe symptoms like irregular heartbeat, chest pain, lung irritation, pulmonary edema and even death may happen.
Formaldehyde exposure can also be classified on the basis of period of exposure. It can be either an exposure for a brief period or a regular one, as in the case of some industrial workers. Regular exposure is said to cause long-term health issues. In case of regular exposure, which is considered as chronic, the person may develop lesions inside the lungs, which may cause lung damage.

Poisonous coloring agentslike, Aurmine, Rhodomine b, Malachite green, yellow g, Allura red

-Damage liver & kidney

-Stomach cancer

-Asthma and

-Bladder cancer

Calcium carbide

Cancer in kidney, liver, skin prostate and lung





Infertility of women


-Damage of kidney & nervous system

-Respiratory problem

Sulfuric acid

-Damage cardiac system

DDT(It is a widely used insecticide, It can enter into the body as food adulterants)

-DDT at concentration of 236 mg per kg of body weight is lethal to the body while at concentration of 6-10 mg/kg leads to such symptoms as headache, nausea, vomiting, confusion, and tremors.

-Long term exposure to DDT may affect the liver.

-Short term exposure to DDT in food may have a harmful on effect on reproduction.

-Oral exposure to DDT can cause liver cancer.

Melamine(an organic base and a trimer of cyanamide. Melamine is sometimes illegally added to baby food products in order to increase the apparent protein content. Standard tests, such as the Kjeldahl and Dumas tests, estimate protein levels by measuring the nitrogen content, so they can be misled by adding nitrogen-rich compounds such as melamine)

Permitted Amount of Daily Intake of Melamine

  • European Union : 0.2 mg/kg body mass
  • Canada: 0.35 mg/kg body mass
  • USFDA:  0.063 mg/kg body mass
  • WHO: 0.2 mg/kg body mass

Toxicity of Melamine:Chronic exposure may cause cancer or reproductive damage. Eye, skin and respiratory irritant.” U.S. Food and Drug Administration (FDA) scientists explained that when melamine and cyanuric acid are absorbed into the bloodstream, they concentrate and interact in the urine-filled renal microtubules, then crystallize and form large numbers of round, yellow crystals, which in turn block and damage the renal cells that line the tubes, causing the kidneys to malfunction.

Brick dust

Respiratory problem

Ethylene oxide


Quick Tests for some adulterants in the food
An integrated approach to face this problem requires a strong cooperation by the food industry, food distributors, the scienti?c community, governments, managers and local administrators in order to build consumers’ trust and con?dence.

Table 3. Methods Used to detect Common Food Adulterants

Name of Food Article


Simple Method for detection of Common Adulterants




The presence of water can be by putting a drop of milk on a polished slanting surface. The drop of pure milk either or flows lowly leaving a white trail behind it, whereas milk adulterated water will flow immediately without leaving a mark.



Add a few drops of tincture of Iodine or Iodine solution. Formation of blue color indicates the presence of starch.

Iodine solution is easily available in the medical stores.



Take a teaspoon of milk in a test tube. Add ½ teaspoon of soybean or arhar powder. Mix up the contents thoroughly by shaking the test tube. After 5 minutes, dip a red litmus paper in it. Remove the paper after ½ a minute. A change in color from red to blue indicates the presence of urea in the milk.



Take 10 ml of milk in a tests tube and add 5 ml of con sulfuric acid from the sides of the wall without shaking. If a violet or blue ring appears at the intersection of two layers then it shows presence of formalin.

Formalin enhances the life of milk and thus is added for preservation purpose.


Synthetic milk

Synthetic milk has a bitter after taste, gives a soapy feeling on rubbing between the fingers and turns yellowish on heating



Take 10 ml milk in a test tube and add 5 ml HCl then add 1 gm resorphenol. Then keep it in hot water for few minutes, if red color is appearing then sugar is presence.



Diabetes examination strip immersed in milk, if glucose present then strips color changed.


Hydrogen peroxide

Take 5 ml milk in a test tube add 5 ml alcohol then add 5 drops of rezolic acid. Presence of hydrogen peroxide solution color will be red in color.

Ghee, cottage cheese, condensed milk, khoa, milk powder etc,

Coal Tar Dyes

Add 5 ml of dil. H2SO4 or conc. HCl to one teaspoon full of melted sample in a test tube. Shake well. Pink color (in case of H2SO4) or crimson color (in case of HCl) indicates coal tar dyes. If HCl does not give color dilute it with water to get the color.


Mashed Potatoes, Sweet Potatoes and other starches.

The presence of mashed potatoes and sweet potatoes in a sample of ghee can easily be detected by adding a few drops of Iodine, which is brownish in color turns to blue if mashed potatoes/sweet potatoes/other starches are present.


Vanaspati or Margarine

Take about one teaspoon full of melted sample of butter with equal quantity of concentrated Hydrochloric acid in a stoppard test tube and add to it a pinch of sugar. Shake for one minute and let it for five minutes. Appearance of crimson color in lower (acid) of Vanaspati or Margarine.

The test is specific for sesame oil which is compulsorily added to Vanaspati and Margarine. Some coal tar colors also give a positive test. If the test is positive i.e. red color develops only by adding strong Hydrochloric acid (without adding crystals of sugar) then the sample is adulterated with coal tar dye. If the crimson or red color develops after adding and shaking with sugar, then alone Vanaspati or Margarine is present

Black pepper

Light black pepper

Float the sample of black pepper in alcohol (rectified spirit). The black pepper berries sink while the papaya seeds and light black pepper float.

Black pepper

Coated with mineral oil

Black pepper coated with mineral oil gives Kerosene like smell.

Mustard seed

Argemone seed

Mustard seeds have a smooth surface The argemone seed have grainy and rough surface and are black and hence can be separated out by close examination. When Mustard seed is pressed inside it is yellow while for Argemone seed it is white

Use magnifying glass for identification

Chilies powder

Brick powder, salt powder or talc, powder

Take a tea spoon full of chilies powder in a glass of water. Colored water extract will show the presence of artificial color. Any grittiness that may be felt on rubbing the sediment at the bottom of glass confirms the presence of brick powder/sand, soapy and smooth touch of the white residue at the bottom indicates the presence of soap stone. To a little powder of chili add small amount of conc. HCl and mix to the consistency of paste, dip the rear end of the match stick into the paste and hold over the flame, brick red flame color due to the presence of calcium slats in brick powder.

This test is only for earthy material

Chilies powder

Artificial colors

Sprinkle the chili powder on a glass of water. Artificial colorants descend as colored streaks.

Chilies powder

Water soluble coal tar color

Water soluble artificial color can be detected by sprinkling a small quantity of chilies or turmeric powder on the surface of water contained in a glass tumbler. The water soluble color will immediately start descending in color streaks

Green chili and green vegetables.

Malachite green

Take a cotton piece soaked in liquid paraffin and rub the outer green surface of a small part of green vegetable. If the cotton turns, green, we can say the vegetable is adulterated with malachite green.



-Firstly, the fish will be washed with small volume of clean water.05 ml of washed water (fish) taken into a clean and dry test through a dropper. Add solution No. 1, 15 drops into the fish washed water into the test tube and shake vigorously and wait for 30 seconds. Again add solution No. 2, 15 drops and shake vigorously and wait 30 seconds. Lastly, add solution No. 3, 15 drops into the test tube :(i)   if the color of the solution changes from colorless to PINK OR RED (ii)  if there is no change of color of the solution.

(i)  Formalin is present.

(ii)  Formalin is absent.

Kitchen tricks to expose food adulteration
In a country where official systems set for food safety and prevention are constantly outdone by a booming adulteration business, the onus of safeguarding one's family against contaminated food, unfortunately falls on citizens themselves. From loose packed ground spices, to wet produce such as milk, khoya, paneer, to dry spices and grains, almost everything you can buy has a potential of being adulterated, if purchased from an unauthorized vendor in a box unmarked and tested. While some of these could be less harmful, such as water or bran, chemicals and coloring agents such as Metanil Yellow, Lead Chromate, Sudan Red III, are known to be carcinogenic. Following test asks for the presence of an acid, you could use common toilet-cleaning acid, or easily found citric acid or even lemon juice.



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