Environmental pollution which leads to the chronic exposure from toxic chemicals seem to be an increasing global challenge that is altering the quality of health of many people. There is an alarming number of chemicals present in the environment today which contribute to various environmental health problems, with over 80,000 chemicals registered for commercial use in the United State alone. Monitoring of the the toxicity of these chemicals is a big challenge for developing countries even as
the developed countries are making tough policies to curb the negative effects of the environmental pollution from these chemicals. For countries who do not have the techniques for monitoring pollution from these chemicals and its effect on health, studies have shown that it is possible that certain nutrients and indeed, nutritional status are linked to the change in susceptibility to these environmental pollutants.

Although not fully investigated, there appears to be a connection between nutritional status, nutrients and environmental toxins especially with heavy metals. Scientific evidence have exposed the interconnection between these three. The flip side of this study lies in the fact that individuals are not exposed to pollution from a single source and that the impact of multiple exposure on human health cannot be fully ascertained. This is however, aimed at encouraging the design of quality studies on nutritional interventions for populations exposed to environmental chemicals by nutritionists.  As a growing field, the intersection between nutritional science and toxicology would benefit from the expertise of nutritionists.
This article looks at the ways environmental toxins interact with nutrition. We look at examples of how food may be a medium through which the human body is exposed to toxic chemicals to increase pollution burden. We also look at the interaction between  the absorbed toxins and the body's nutritional status in respect of how it may affect health status by altering nutrient absorption. Also, once inside the body, nutrients and nutrient metabolism may also interact with the toxins to create a specific health outcome. Factors, such as gender and age are also considered because they affect both nutritional status (child-feeding practices) and toxins exposure (mode of feeding).

Food as a source of chronic exposure to harmful environmental pollutants
Toxic chemicals from the environment can be introduced into food while it is being grown, as in the case of use of dangerous pesticides on agricultural products. Also the activities during processing and storage of food products may also influence the increase hazardous chemical content of food. A typical example is the use of coal-burning stoves for drying or smoking food in rural comunities. This activity is among the top in the sources of arsenic pollution in food. Another typical example of food pollution from environmental sources is the exposure of fishes and seafood to methylmecury where inorganic mercury undergoes methylation in water and accumulates in the fatty tissues of food.

Prospective studies into early postnatal exposure from seafood in New Zealand has been linked to cognitive deficits in children, including attention and perceptual deficits, and general cognitive deficits. Although this findings have been are termed controversial based on the lack of enough evidence in other popular fish-eating regions, there is increased concern in pregnant woman about the potential harm from prenatal exposure to methlymercury.

Already, current recommendations in the United States call for reduced consumption of seafood during pregnancy. But such recommendations may be difficult to implement in developing, low-income, fish-consuming countries where a change in diet may affect both economic status and create a conflict for individuals who view fish and seafood as a rich source of fatty acids which is necessary for brain and heart development.

Nutritional deficiency increases effects of environmental pollution in the body
Most cases associated with lead exposure has been linked with nutritional deficiencies, just as cognitive disorders in children exposed to lead pollution (even at levels previously thought to be harmless) is common among disadvantaged populations. This may be primarily due to the interaction between Lead pollution and micro nutrients at the point of intestinal absorption, brain neurochemistry and cognitive functions. Research evidences show that Iron and Lead share a common intestinal transporter (divalent metal transporter 1) and this has led to the belief that iron deficiency increases the rate of Lead absorption in the intestine.

Furthermore, research studies have shown that adult women and children with higher amounts of dietary calcium intakes have lower concentrations of Lead in the blood. Also, it has been observed that the transfer of Lead through the placenta to the fetus was lower in women who take diets rich in Iron and have high hemoglobin levels.

Although primary prevention to Lead exposure may be feasible, this may not be the case when Lead pollution sources are either unknown or not under the control of environmental pollution observers. In this case, perhaps, only nutrients supplements may minimize the harmful role Lead plays in the health of children. This thought was amplified in a study which examined the potency of Zinc, Iron and Calcium supplements in reducing the levels of Lead concentration in blood in children. Results showed that Iron and Calcium had positive impact. However, some studies have cautioned against relying on Calcium as the sole treatment for Lead toxicity.

In adults, a study by Dr. Ettinger of the Harvard School of Public Health, presented evidence on Calcium supplementation as a means of reducing bone reabsorption and Lead concentrations in blood of pregnant and lactating women, as well as the impact of supplemental Calcium on breast milk Lead concentrations. This overview was based on a series of ongoing cohort and intervention studies conducted in Mexico City. The Mexican interventions constitute the bulk of existing data on the efficacy of Calcium supplementation in reducing maternal Lead burdens.

Environmental pollution from Cadmium (which is associated with kidney toxicity) has been recently discovered to decrease bone density and increase fractures even at low levels of environmental exposure, especially in women.  Tobacco smoke is a major source of cadmium-related health defects but some food sources have exhibited relatively high levels of cadmium pollution. They include rice, legumes, cereals, shellfish and leafy vegetables. Cadmium mimics the absorption pattern of Iron, Calcium and Zinc inthe intestine. Studies have revealed that low Iron intake increases the absorption of Cadmium in the body. There is some speculation that the absorption of Cadmium may increase at very early stages of Iron deficiency, even before increased iron absorption is observed.

Nutrient deficiency and environmental toxins have similar outcomes
Arsenic exposure has been identified in drinking water is countries such as India, Bangladesh, Mexico, Argentina and Vietnam with hundreds of millions of people likely exposed to arsenic pollution at levels above 100g/L (well above the WHO drinking water standard). Other environmental sources of arsenic pollution include coal-burning stoves and contaminated food. Arsenic pollution has been linked with increased lung and bladder cancer even at moderate exposure. It may also be linked with diabetes mellitus and hypertension in individuals with high exposures.  In children, arsenic exposure is associated with low IQ scores and memory loss, not to mention fetal and infant death. Interactions between arsenic and nutrient status and metabolism on health outcomes have been documented. One study links nutrients, one-carbon metabolism and arsenic toxicity in Bangladeshi women.

Malnourished women of reproductive age and young children, may be more susceptible to adverse health effects of environmental chemical exposures. The very nature of children's growth and development also makes them vulnerable to both nutritional deficiencies and exposures from toxic chemicals. A recent study analysed neurodevelopmental disorders caused by environmental chemical exposures as a modern “silent pandemic” in children. This places a large portion of the World's children, especially in developing countries, at risk of not reaching their optimal health and development.

Women of reproductive age are also susceptible to nutritional deficiencies, especially during pregnancy when maternal and fetal growth requires high nutrient demand. Nutritional deficiency may create a situation where the mother may become a source of chemical exposure to the fetus or infant via placenta exchange or breast feeding. Environmental exposures in women of reproductive age are especially precarious because women may become sources of exposure to their fetuses and infants through placental exchange and breast milk.

The fraction of diseases caused by environmental exposures may be small, but the above considerations relates to the importance of toxic chemicals in affecting health. It should be noted that small risk factors may contribute to a disease when a large part of the population is exposed to harmful chemicals. Also these environmental toxins are present at almost every developmental stage in our lives so they can accumulate to cause lifetime illness. Third, if chemical exposures interact with poor nutrition, the result may be high costs to health and well-being of poor individuals and communities who are least able to cope with those costs. Better understanding of the interactions between nutrition and environmental exposures is needed to guide action from governments and individuals concerning the effects of nutritional interventions as an approach to preventing or reducing toxicity.

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