Sea Pollution and Human Health

Many waste substances that have been disposed of into the sea can cause a variety of acute and chronic health conditions. The concentration, biological form, chemical form, physical form and survival of these pollutants are all aspects of whether humans would be exposed to them. There are two major ways in which humans can be contaminated by these pollutions. The first is direct contact either through the skin, lungs or by being digested; swimming in polluted sea water would be a good way of being contaminated by a direct contact method. The second way is an indirect way such as consuming plants or animals that have come from the contaminated area. Indirect contamination is a significant way in which humans can be exposed to toxic organic chemical and metals because they can be bio accumulated in plants and animals that humans consume. Direct contamination is a less significant way in which humans can be exposed to toxic organic chemical and metals because they tend to be in sea water in low concentration. In the case of pathogens both methods can be significant because only small numbers of micro organisms to induce disease and because micro organisms can reproduce in infected animals and the environment. 'Conservative' and 'persistent' pollutants such as toxic metals and PCB's are broken down slowly if at all, while 'non conservative' and 'labile' pollutants such as biodegradable or volatile organic chemicals are rapidly broken down and removed from the environment. The 'conservative' and 'persistent' pollutants are the most problematic due to their environmental persistence enhances their chances of reaching and affecting humans. There are three main categories of pollutants in the sea that can reach and have adverse affects on human health. First toxic metals such as arsenic, cadmium, lead and mercury, secondly synthetic organic chemicals such as polycyclic aromatic hydrocarbons (PAHs), chlorinated hydrocarbons, pesticides (dioxins), 'specialised' chemicals polychlorinated biphynyls (PCBs) and thirdly human pathogens such as viruses, bacteria, fungi and parasites. Metals are chemical elements and cannot be destroyed, broken down or degenerated in the environment. Toxic metals that have been disposed of in the sea have impacts concerning human health, especially arsenic, cadmium, lead and mercury. These four metals are particularly of concern because they are known to be toxic to human health and have been found in high concentration in river estuaries and the sea. Chromium, selenium and copper are found in less concentrations but are still of concern because they are in areas that come in contact with humans. Consumption of contaminated seafood is the major indirect route of human exposure to toxic metals. Marine organisms such as fish, crabs and shellfish bio accumulate these toxic metals through their gills when swimming and feeding on matter than have been contaminated. Arsenic, cadmium, lead and mercury can cause acute and chronic conditions including gastrointestinal haemorrhaging, comas, liver and nerve damage, skin and lung cancer, emphysema, anaemia, kidney, liver, pancreatic damage, bone damage, blood disorders, reproductive disorders, eye damage, respiratory impairments and skin lesions. Organic chemicals are used in industry; these chemicals are used in pesticides, cosmetics, drugs and food additives. The behaviour of these chemicals in natural environments vary form accumulating in organisms to not, from decomposing rapidly when exposed to light, heat or water to being very resistant and from being metabolized by other organisms into compounds that are more or less toxic to resisting bio-degradation. Like toxic metals, organic chemicals have direct and indirect routes to affect human health, direct through contact with organic chemicals and indirect by ingesting contaminated animals and plants. The direct route of contact in the sea is rare as organic chemicals are only in low concentration; this method provides no ill effect on human health because of the low concentrations. Again, as with toxic metals the indirect route of consuming contaminated seafood would be the most harmful to human health. Chlorobenzenes, chlorinated pesticides, chlorinated hydrocarbons and aromatic hydrocarbons have all been found in seafood. These chemicals all have adverse human health effects such as causing cancer, skin and liver disorders. Human pathogens are micro-organisms that are capable of inducing human diseases. Human pathogens enter the sea from the discharge of raw sewage, sewage sludge and wastewater effluent from sewage treatment plants. Pathogens are also found in commercial and domestic food waste, animal waste and biological waste from hospitals and laboratories. Many of these pathogens are discharged to surface waters or sewage treatment plants. In rural areas, bacterial contamination animal waste, runoff and poorly treated sewage discharge. The sea itself is a source of pathogens which occur and propagate naturally in marine waters. Viruses and bacteria are the most important of waste-borne agents of human diseases with respect to their concentration in waste and the environment and to diseases they cause. Both direct and indirect exposures to humans are significant ways of effecting human health. This is because only a small number of organisms are required to induce disease. Evidence has shown that some bacteria, including known human pathogens can survive in the sea for up to three months. Many parasites and viruses are very resistant to environmental destruction. Many human pathogens appear to survive better in coastal or estuary region than open ocean. Large areas of coastal or estuarine waters in the US have been closed to shellfish fishing due to contamination by sewage borne micro-organisms. Shellfish borne bacteria diseases have been responsible for typhoid, paratyphoid, cholera and viral gastroenteritis outbreaks in the US. Some bacteria diseases such as typhoid have been contracted by swimming or surfing in water that is contaminated with sewage. Many scuba divers have been affected by conditions such as dermatitis, wound infections and enteric illnesses. In conclusion, it is best to eat fish and seafood that we know has come from the open ocean or from estuarine and coastal regions that have not been contaminated from industry or human waste. It is also wise to participate in water sports in areas that you know have not been contaminated by sewage or industrial waste.