Arsenic Contamination in Food Chain

Arsenic (As)

• Arsenic is a naturally occurring trace element that occurs in many minerals, usually in combination with sulfur and metals.
  • It can also exist as a pure elemental crystal. 
  • It is a metalloid and has various allotropes.
  • Only the gray form, which has a metallic appearance, is important to industry.
• Arsenic has been recognized as a toxic element and is considered a human health hazard.
• It can occur in both organic and inorganic form.
  • Inorganic arsenic compounds (such as those found in water) are highly toxic 
  • The organic arsenic compounds (such as those found in seafood) are less harmful to health.
• It is now recognized that at least 140 million people in 50 countries have been drinking water containing arsenic at levels above the WHO provisional guideline value of 10 μg/L.

Permissible Limits

• The World Health Organization’s provisional guideline value for arsenic in drinking water is 0.01 mg/l (10 μg/l).
• The permissible limit of arsenic in India in the absence of an alternative source is 0.05 mg/l (50 μg/l).

Health hazards due to Arsenic

• Acute effects:
  • The immediate symptoms of acute arsenic poisoning include vomiting, abdominal pain and diarrhoea. 
  • These are followed by numbness and tingling of the extremities, muscle cramping and death, in extreme cases.
• Long-term effects:
  • Affects Skin and can lead to Skin Cancer
    • The first symptoms of long-term exposure to high levels of inorganic arsenic are usually observed in the skin, and include 
      • pigmentation changes, skin lesions and hard patches on the palms and soles of the feet (hyperkeratosis).
    • These occur after a minimum exposure of approximately 5 years and may be a precursor to skin cancer.
  • Bladder and Skin Cancer
    • The International Agency for Research on Cancer (IARC) has classified arsenic and arsenic compounds as carcinogenic to humans.
      • It has also stated that arsenic in drinking-water is carcinogenic to humans.
  • Developmental Effects, Diabetes, Pulmonary disease & Cardiovascular disease
    • Arsenic-induced myocardial infarction, in particular, can be a significant cause of excess mortality.
    • In Taiwan, arsenic exposure has been linked to “Blackfoot disease”.
      • It is a severe disease of blood vessels leading to gangrene.
  • Adverse Pregnancy Outcomes, Infant Mortality and Child Health
    • Exposure in utero and in early childhood has been linked to an increase in mortality in young adults due to 
      • multiple cancers, 
      • lung disease, 
      • heart attacks, and 
      • kidney failure. 
    • Numerous studies have demonstrated negative impacts of arsenic exposure on cognitive development, intelligence, and memory.

Sources of Arsenic and exposure

• Drinking water and food: 
  • The greatest threat to public health from arsenic originates from contaminated groundwater. 
  • Inorganic arsenic is naturally present at high levels in the groundwater of a number of countries, including Argentina, Bangladesh, Chile, China, India, Mexico, and the USA. 
  • Drinking-water, crops irrigated with contaminated water and food prepared with contaminated water are the sources of exposure.
  • Fish, shellfish, meat, poultry, dairy products and cereals can also be dietary sources of arsenic.
• Industrial processes: 
  • Arsenic is used industrially as an alloying agent, as well as in the processing of glass, pigments, textiles, paper, metal adhesives, wood preservatives and ammunition.
• Tobacco and smoking: 
  • A person who smokes tobacco can also be exposed to the natural inorganic arsenic content of tobacco. 
    • It is because tobacco plants can actively take up arsenic naturally present in the soil.
• Earth’s crust: 
  • Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment in the air, water and land. 
  • It is highly toxic in its inorganic form.
• Volcanic action: 
  • Around 1/3rd of the arsenic in the Earth’s atmosphere is of natural origin. 
  • Volcanic action is the most important natural source