ISSN: 0972-1266
Industrial Toxicology Research Centre, Lucknow (U.P.)
Vol. 9
May 2002

  1. Chromium & Occupational Exposure
    Of Tannary Workers
  2. Unintentional Health Hazard
  3. Dioxins Contamination of
  4. Heavy Metal Contamination Of Food
  5. Current Concerns
  6. Regulatory Trends
  7. In a Lighter Vein
  8. Miniprofile of Mercury
  9. On The Web
  10. Book Stop
  11. Conference Diary

During the early 20th century most substances that people were likely to encounter in their daily lives were derived with little modification from the earth, the animals, vegetables, crops or the mineral sources. Today there is an extensive existence of synthetic chemicals in the environment, a class which was not present until their creation by human scientific and industrial efforts. The domination of chemicals is increasing in our lives-can we imagine life without agro-chemicals, pharmaceuticals, preservatives, disinfecting agents, colorants, plastics etc.? Regrettably, this dependency on chemicals has resulted in too many cases of their misuse, especially in their disposal, or mal-or over-use in agriculture. Chemicals such as phthalate esters and polychlorinated biphenyls are considered to disturb human hormone messengers and effect fetal reproductive development. Reckless use of chemicals, careless disposal of chemical wastes causing ecological imbalance, and the lack of farsightedness contribute to a global threat. A major concern has been the prevalence of the common environmental contaminants in food,that is,pesticides and heavy metals. These metals, even if occurring in low concentrations pose a threat of being bioconcentrated and magnified in the higher trophic organisms of the food chain after being used for human consumption.National programmes to create mass awareness on pesticides and other food contaminants, and to assess their environmental impact, need to be launched and sustained.

It is an irony that the very disinfectants used for purifying drinking water can also be hazardous. Although unintended, chemical disinfection by-products cause health hazards. Numerous workshops and conferences have been organised by international bodies like EPA, CDC, NCI etc. to address these new health concerns.

Odds & Ends
Chromium and Occupational Exposure of Tannery Workers

Basic chromium (III) sulphate is widely used in the leather industry as basic tanning agent. The tannery workers are exposed to this element, mainly in the inorganic Cr (III) form or in the protein bound form (leather dust). Workers from tanning and retanning departments showed an inverse relationship between urine chromium and hemoglobin. Kornhauser and co-workers from Universidad de Guanajnato, Mexico observed lower urinary excretion of iron with increasing chromium serum in these same subjects. Their results suggest an adverse effect of chromium which is related with iron metabolism alterations and which can be observed in subjects with excessive chromium accumulation in the organism. They have recommended chromium urine test for the diagnosis of the observed adverse effect, but have also suggested the need for further studies to characterize quantitatively the relation between urinary excretion and the hemoglobin alterations.
( Ind. Hlth., April, 2002).

Unintentional Health Hazard

It is an irony that the chemical disinfectants used for purifying water can also be hazardous. Although pathogenic organisms provide the primary health risk from drinking water, chemical disinfection byproducts (DBPs) are another, albeit unintended health hazard. Disinfectants are powerful oxidants that convert organic matter and naturally occurring bromide in source waters to DBPs. Chlorine, ozone, chlorine dioxide and chloroamine are the most common disinfectants in use today, and each produces its own group of chemical DBPs in drinking water.

After the identification of the first DBPs, chloroform and other trihalomethanes (THMs) in chlorinated drinking water in 1974, an important public health and regulatory issue was born. Today, many drinking water utilities are switching from chlorine to alternative disinfectants such as ozone, chlorine dioxide, and chloramine in order to control THMs and haloacetic acids (HAAs), but this has created new issues. Source water conditions, including bromide, iodide, and natural organic matter (NOM) concentrations, and pH, can affect the levels and types of DBP species formed. For example, ozone use can significantly reduce or eliminate THM and HAA formation, however, it can produce bromate,a potent carcinogen in laboratory animal in source waters with elevated bromide levels.

DBPs that have been quantified in drinking water are generally present at nanogram to microgram per liter levels. Another concern is that although ~ 500 DBPs are known, few have been investigated for their quantitative occurrence and health effects. However, there are still unknown DBPs; only ~ 50 % of total organic halide (TOX) formed during drinking water chlorination has been identified. Studies are underway to uncover the missing DBP fraction, such as unidentified TOX and assimable organic carbon compounds in ozonated water. Numerous workshops and conferences have been organised to address the concern about-DBPs and new human exposure work is also being conducted (at CDC, NCI, EPA and other laboratories) in which blood and urine are being monitored for DBP.

National Cancer Institute (NCI) had linked chloroform to cancer in laboratory animals. DBPs effects on reproduction and development, including low birth weight, intrauterine growth retardation, spontaneous abortion are raising new concerns.
(Environ.Sci. Technol., May, 2002).

Dioxin Contamination in Food

Dioxins are a heterogeneous mixture of chlorinated dibenzo-p-dioxin and dibenzofuran congeners. They are highly toxic by-products of incineration processes and of production of chloro-organic chemicals. Accidental poisonings have occurred repeatedly, the main human exposure being via the dietary route. Ruminants accumulate the dioxin emissions which are released mainly through industrial and municipal incineration and pyrolysis processes. Cow's milk and milk products, bovine adipose tissue, hen's eggs and fish are the main contributors to human dioxin exposure in adults. The highest exposure in the human population occurs in infants via breast-feeding.

So far there are no reports to show that acute toxic responses occur in humans under normal dietary habits generating background dioxin body burdens. Also no signs of chronic toxicity have been reported under these conditions. However, there are reports from accidentally highly exposed workers who had an increased incidence of infectious diseases suggesting a weakened immune system.

Species comparison for dioxin body burden and effects based on adipose tissue concentrations conducted by W. Parzefall of the

University of Vienna, Austria, lead to the conclusions that (a) toxic symptoms are observed in rats and humans at similar endogenous dioxin concentrations (b) meals of high dioxin content will increase human body burden. (c) a single high intake by a normal adult individual does not pose any health risks. In any case, repeated intake of dioxin contaminated food must be avoided.
(Fd. Chem. Toxicol., 2002)


The common environmental contaminants of greatest concern in food are heavy metals, most notably cadmium, lead and mercury. Unlike some other metals these have no known beneficial nutritional value for humans, play no known role in metabolism, as no enzyme has been identified which specifically requires cadmium, lead or mercury as a cofactor. Among these two metals are however, extremely hazardous to life and have been involved in historic poisoning episodes of human populations and wildlife resulting from ingestion of contaminated foods and prey. The concentrations of cadmium and mercury are increasing in both anthropogenic inputs, and this continues to be a concern to toxicologists. The importance of individual food types as sources of Pb, Cd and Hg in the diet indicate fruits and vegetables as the biggest sources of Pb and Cd and sea food the biggest source of Hg. Heavy metals content of cooked foods, milk and water are also higher in certain areas. Contents of heavy metals were determined in raw milk samples obtained from 3 regions of Turkey differing in environmental pollution. Highest heavy metal concentrations were generally found in milk samples from the industrial region, followed by the intense-traffic region.

In recent years recycling in agriculture is a common method of disposal or utilization of waste. In general, raw sewage effluents, sludges and sewage-irrigated soils contain very high amounts of cations, anions, organics and heavy metals. Dispersion by leaching of the metals from irrigated soil and from settled bottom sludge in wetland sewage channels are the principal cause of groundwater contamination. A dietary survey was carried out on men from low and medium income groups belonging to sewage and tube well irrigated areas and were found to be more than WHO tolerable limits. Crops especially garlic, leafy vegetables grown in sewage water irrigated areas were found to contain higher concentration of Pb, Cd and Ni than those grown in tube well irrigated soils. Activated sludge, recommended as a cheap supplement in cattle and poultry feed is also contaminated with heavy metals along with pesticides and organic pollutants. In a study this sludge was found to contain Zn (1.82 mg/g), Ni (0.27 mg/g), Pb (0.17 mg/g), Cu (0.05 mg/g), Cr (0.006 mg/g) and Cd (0.005 mg/g). Even though sludge is a rich source of nitrogen matter, its supplementation in poultry and animals feed should be done cautiously otherwise, the metal contaminants in sludge biomagnify in the food chain.

Uptake of heavy metals in farmers fields varied widely among species and parts of plants. In many plants the roots tended to retain heavy metals more than foliage or above ground plant parts. Rice samples from 15 areas of Asia had been analyzed for Pb and Cd content. A study conducted in South India showed rice to be a major source of Cd and Pb among the rural population and economically deprived class. Concentration of Cd, Pb and Hg in organically grown grain (wheat, barley, millet, buckwheat, peas, mixed grains) and milled products ( wheat flour and bran ) obtained from 1993 and 1994 harvests in the Czech Republic were lower in organic samples than in corresponding crops grown in the same year by conventional intensive farming methods. In a survey by the Indian Council of Medical Research, a total of 198 samples of 20 brands of infant formula milk were collected from retail shops in and around Pune, Mumbai, Mysore, Lucknow and Ludhiana, and analysed for pesticides and metals. The study indicated high levels of metal contamination (As, Cd, Pb, Cu and Zn).

Heavy metals, even if occurring in low concentration pose a threat of being bioconcentrated and magnified in the higher trophic organisms of the food chain after being used for human consumption. Water samples from hand pumps, dug well, spring, stream and river were assessed for heavy metals. Hand pump water sample exhibited the highest degree of metal contamination.

A monitoring survey for Hg, Pb and Cd in a range of sea food (fish, bivalves and cephalopods) indicate that Pb bioaccumulation in marine food chains is declining. Hg levels determined in fish samples showed considerably less variation than Cd levels, indicating that Hg is being readily bioaccumulated in marine food chains. It is concluded that effective measures should be implemented to restrict levels of Hg and Cd entering the marine environment and human diets.


Lead has been recognized as a health hazard for centuries. One of the most studied metals, much information has been accumulated on its toxicity which is caused by acute or chronic environmental exposure is a constraint to the control, reduction, prevention, and intervention strategies although because of health concerns, lead from gasoline, paints, ceramic products and pipe solder has been dramatically reduced. Dietary exposure of it falling as a result of measures taken to reduce Pb contamination of the environment and food UK population ( 0.026 mg/day ) to Pb. The major sources of lead in drinking water are lead plumbing, soil carried into water by rain and wind, pesticides and fertilizers and wastewater from industries that use lead. Most individuals ingest lead almost daily via food which can contain lead by dust deposition on crops while growing or through food containers. Lead has been used for centuries as glazing and for the bright colours on ceramic pots and dishes. The amount of Pb that leaches from a dish depends on how the dish is used and the kind of food stored in it. Acidic food and drinks will leach Pb out of the dishes much faster than non acidic foods. The longer the food stays in contact with a dish surface, more the chances of Pb leaching into the food. Heating up food in Pb containing dish can speed up the Pb leaching process. However, the major exposure of Pb to the general population in food is through grains, vegetables and fruits.

Exposure of General Population through Pb Contamination in Food