THE GARBAGE DUMP OF THE SHIPS (PART TWO)

Marine refuse is generated aboard freighters, fishing ships, cruisers, recreational yachts, military ships and research vessels altogether, besides the polluting sources from the mainland. Marine waste is conformed by a very assorted variety, which includes glass, plastic, metal, paper, fishing equipment, linen, food leftovers, wood, rubber and packing materials.

Marine garbage has a long span of life and can stay active for decades in a direct or in an indirect sort of way. It is mostly composed of plastic items, but also of metal and glass, just to mention two other neither easily nor rapidly degrading materials. Plastic junk can also be a source of resilient organic substances.

For a long time, people believed that the oceans could be able to absorb and cope with anything. Nevertheless, time has proven otherwise, our attitude towards this problem has changed, and we have learned to be more and more concerned about the environmental problems. Oceans can deal with and decompose a lot of objects and materials, but this process can take months or even years, as is shown in the following listing:

Orange and banana skins	up to two years
Cigarette filters	5 years
Wool stockings	1 to 5 years
Painted wood	13 years
Plastic coated paper	5 years
Plastic bags	10 to 20 years
Plastic containers	20 to 30 years
Nylon fabrics	30 to 40 years
Leather	up to 50 years
Cans	100 years
Aluminium cans	200 to 500 years
Glass bottles	One million years
Plastic bottles	Indefinitely

The using of synthetic and non bio-degradable materials in fishing apparels and packing devices brings a high rate of death to maritime mammals (dolphins, whales, seals, sea otters, manatees and many others), birds, fishes and other species, in both a local and a global extent.

Even though they are not one the most affected groups, marine mammals have been well documented and some of its species are more endangered than others. A recent research made by the Bureau of Technology of the Congress of the United States of America reached the conclusion that an approximate number of one hundred thousand marine mammals die every year throughout the oceans of the world as a result from the ingestion of plastic debris or by getting trapped into them. This situation is getting worse by the day. This kind of death is neither fast nor kind at all.

There are three different ways with which fish and marine mammals can find death by getting entangled into garbage. If the fragments are big enough as to immobilise them, animals would drown or suffocate. Medium sized fragments will cause tiredness and death by hunger, due to the extra weight they would have to drag with them. Small fragments, which conform the largest numbers of garbage objects, comprise packing tapes, cords, and other small materials. They are slow killers, which could even take months in order to accomplish their deadly task, by slowly strangling or by cutting the animal's flesh while it grows up in size.

The swallowing of plastic garbage has been registered in birds, tortoises, fish and marine mammals; this garbage ranges from pellets to bags. Inside the corpse of a young pigmy whale that died at the shores of Texas in 1993, it was found that the first two stomach compartments were full of plastic litter, including a garbage bag, a bread wrapping, a French fries bag and two other plastic fragments.

The objects that are mostly ingested by whales and dolphins are plastic bags and sheets, although other items as nets, cords and other samples of plastic objects have been retrieved from these animals' vowels.

There are 69 bird species around the world that are known to swallow plastic debris. The commonest of these materials are small plastic pellets (measuring between 0, 2 and 0, 6 millimetres of diameter). Next in line come the polyethylene fragments. Polystyrene objects are found in smaller quantities. Plastic pellets are a prime material which is obtained from synthesised petrochemical substances. They are shipped in bulks to the manufacturing centres were they will be melted and turned into products for the public's use.

The ingestion of large quantities of plastic objects could bring an obstruction of the intestines, a false sensation of fulfilment or reduce the amounts of nutrients absorbed by the body. Species unable of regurgitating can also absorb toxic substances released by accumulation.

Birds can also get knotted into domestic garbage and fishing waste. The objects with which birds most commonly use to get entangled with are those six-pack plastic rings. Many birds gather pieces of fishing nets to build their nests, these nets could turn out into awaiting traps that may strangle any of the parents or their chicks.

Recent researches had outlined one type of plastic poisoning which has been previously overlooked: small fragments of plastic called "scrubbers" (spheres) with an average diameter of half a millimetre each, a side-product from hand cleaners, cosmetic compounds and compressed-air cleaning products.

The compressed-air technology uses polyethylene particles to wipe out all traces of paint from metallic surfaces and to clean mechanical pieces. These particles can be re-used some ten times before being disposed off, and when this happens, they are sometimes contaminated with heavy metals. The impact these resilient particles can bring to the environment can be of varied natures. For example, heavy metals or other contaminants can get transferred to filtering organisms or other invertebrates and attain high levels of toxicity.

Floating plastic debris could represent possible ways for the invasion of foreign species: Plastic objects that drift through the sea can be the hosts to many organisms as bacteria, diatomite and algae among other micro-organisms. Hovering plastics could raise the numbers of marine organisms or introduce new species into another marine environment.

Residual waters, sewage waters or "black waters" are the names generally given to water refuse from bathrooms, medical sinks and other alike installations. They are commonly regarded as an item apart from the "grey waters". Ships use to dispose of these waters by throwing them into the sea, whether having them previously treated or not.

Untreated waters from the ships show by a general rule higher concentration rates of manure and toxic wastes than domestic ones, because aboard ships water is used in smaller amounts to wash out refuse. Residual waters from the ships carry harmful micro-organisms along with excessive concentrations of nutrients to the marine environment.

Moreover, some chemical substances as chlorine, ammonium and formaldehydes are commonly used for solving organic elements in many Marine Sanitary Devices (MSD) which are harmful to marine life forms. What is worse, many of the ships that do employ the MSD, are not always willing to treat their residual waters with the required and proper levels.

"Grey waters" come from showers, sinks, washbasins and kitchens, containing contaminating agents as oils and greases, pesticides, soap, detergents, metals and cleansing products. The elements contained by "grey waters" could negatively affect the life and the marine environment, because it lessens the degrees of solved oxygen, not to mention its toxic contents.