prn8099 - Number 13, June1997

Beginning from July 1, 1997, the Seberang Perai Municipal Council (MPSP) will be pioneering a courageous move towards the preservation of the environment. On this date, MPSP undoubtedly will be the first municipal council in Malaysia to restrict the use of plastic packaging in areas under its jurisdiction. Such a visionary move will go a long way to reshape the norms and attitudes of Malaysians towards the use of plastics, a common material often taken for granted by many. They are no doubt convenient but at what cost?

Enormous research in the environmental effects of plastics have shown that these materials are relatively inert and not degradable, unlike wood, paper, natural fibres or even metal and glass. In other instances, plastics which were thrown indiscriminately into the ocean and other water ways have resulted in the the suffocation and death of sea animals such as turtles and dolphins.

The move by MPSP should therefore be welcomed and supported as we move towards achieving the status of a developed nation by the year 2020. Indeed, most industrialised countries right now have either banned or restrict the use of plastic packaging so as to reduce the environmental degradation resulting from it.

Globally, new environmental regulations, societal concerns and a growing environmental awareness throughout the world has triggered a paradigm shift in developing products and processes which are compatible with the environment. In tandem with this awareness, a new concept of designing materials from Cradle to Grave has been proposed which integrates material design concepts with ultimate disposability, resource utilisation and conservation.

At present, plastic materials have been considered to be an essential part of modern living due its features of strength, light-weight, being inexpensive, easily processable and energy efficient. With their inert properties, plastics are widely used as packaging materials as they maintain the purity and freshness of the content as well as protecting it. Since World War II, plastic proved to be a rich source of acceptable substitute for various sources of natural materials such as rubber, silk and many metals. The packaging industry is the leading user of plastics accounting for about 40% of the total world plastic production.

Million of tons of packaging are discarded as solid waste each year. In a survey among the developed countries, an average of 398 kg of domestic waste are generated annually by each person. Although the content of plastic materials in a municipal solid waste (MSW) has been estimated in the range of 7-12 % by weight, the proportion contributed by volume from them ranges from 18-30 % of the solid waste. This increase in the proportion of the plastics is due to their inherent low density and thus requiring larger landfill areas. An estimate on the continuous amount of plastic being thrown away as domestic waste showed that out of 20,000 million kg of resin products made a year, 12,000 million kg (60%) would end up as MSW.

Among the various solutions offered to the increased volume of plastics, incineration and recycling appear to be the most promising on technological and economic grounds. Incineration, unfortunately, is proving unfriendly to the environment. It is obvious that recycling alone will not be sufficient to handle all of the post-consumer plastic waste expected over the next decade. According to another estimate, by the year 2000, no less than 3 billion kg of thermoplastics like high density polyethylene (HDPE), polyethylene terepthalate (PET) and low density polyethylene (LDPE) are expected to be recycled representing a mere 7% of the total stock of post-consumer plastic waste. The other 93% will still continue to be discarded in landfills unless another solution can be found.

In Malaysia, the method of disposal for municipal solid waste particularly has been largely through landfilling (90%) with a very little share of recycling (8%) and incineration (1-2%). As it becomes increasingly difficult to obtain new landfill areas due to the awareness of the lay public through the phenomenon called not in my backyard, two alternatives remain, namely waste reduction either by recycling or the use of degradable plastics.

Looking at the scenario globally, the distribution of MSW in future is expected to change with the aim of reducing the overall amount of MSW production through education and home composting. Home composting is an ecologically and environmentally sound approach to transfer biodegradable waste into useful fertilisers. The European Communities (EC) for example, has set the disposal method: 55% through recycling and composting, 35% through incineration and about 10% through landfilling. Promotion of Biodegradable Plastics The development of biodegradable plastics can play a crucial role in helping solve our waste disposal problems. Since waste reduction is important for future municipal solid waste, a number of important issues need to be addressed to ensure that new biodegradable plastics industry develops. Today, the main obstacle to widespread use of biodegradable plastics is cost. In the United States, biodegradable plastics are priced at $2.50-6.00 per pound of the resin which is about five fold higher as compared to the common thermoplastics. Due to their high prices, most current applications for biodegradable plastics are in niche packaging area with unique environmental considerations. Other factors which will be important in determining the future growth of biodegradable plastics include the following:

• Regulatory Actions

The development of the biodegradable plastics industry in the US has demonstrated that unfounded claims were made on the material being used as biodegradable plastics. The first generation of allegedly biodegradables i.e. starch filled polyolefins have been shown to be actually a non-biodegradable material. This material could at best be described as biodisintegrable and not completely biodegradable. Data showed that only the surface starch biodegrades leaving behind a recalcitrant polyethylene material. In addition, starch entrapped within the polyethylene matrix did not appear to be degraded.
Based on the above development, a number of regulatory actions resulted which among others define the biodegradability of a product taken as 'the properties of the material when exposed to a waste management facility that is, designed to ensure biodegradation and the product at issue will safely break down at a sufficiently rapid rate and with enough completeness when disposed of in that system'. Moreover, the breakdown products of the biodegradation process should be non-toxic and should not build up in the environment at a faster rate than they are being utilised by the microorganisms.

• Incentives for research and development on biodegradable plastics

Scientific research into biodegradable plastics is important for the technology in plastic waste management to go forward. New approaches, new products and new developments are needed to ensure further growth into this area. At Universiti Sains Malaysia, a multi-disciplinary research approach has been initiated to develop biodegradable plastics using locally available resources. The progress achieved thus far is described below:

Biodegradable Plastics Research at Universiti Sains Malaysia

The emphasis of the research is on the production of a group of bacterial polyester identified as poly(hydroxyalkanoates) from palm oil, a renewable resource and one of Malaysia primary commodities. The research group has been able to isolate a number of local microorganisms which has been shown to produce a widely used standard plastic for biodegradability namely, poly(3-hydroxybutyrate). The results has so far indicated that palm oil is an efficient raw material for the production of the plastic as compared to the common raw material, glucose, being used to produce the plastic at the industrial scale. The theoretical biochemical pathway from palm oil has indicated that the local substrate is capable of producing the plastic about three times higher than the carbohydrate source. For 1997, the project has acquired a 100 liter fermenter to study the aspect of pilot-scale production of the plastic before embarking into the large industrial scale production. The biodegradable plastic research group has been funded through research grants from the Malaysian government since 1990. Further research is now being conducted to identify the genes responsible for the production of the plastic inside the microorganism. Besides this, the development of a standard biodegradation testing would also be carried out to ascertain the mechanism of biodegradation under the local tropical condition.

• The standard development activities

The issue of standard specifications for biodegradable plastics needs to be conducted by an independent and well represented committee. The test methodology to measure the intrinsic biodegradability should take into consideration the local environmental condition as well as the local microbial organisms. Inclusive in the test methodology, the test methods to stimulate the environment that are representative of waste management infrastructure on a laboratory scale. Parallel tests in real world systems need to be run to confirm and establish biodegradabiltiy. To harmonise the various standards for biodegradation, evaluation of the various standards such as Sturm test for Ready Biodegradability, the Japanese MITI test for biodegradation and the American Standard Organisation, ASTM standard for intrinsic biodegradability of plastic materials under an aerobic and anaerobic environment should be performed as well.

• The need to increase for composting infrastructure

Composting can be defined as "accelerated degradation of heterogeneous organic matter by a mixed microbial population in a moist, warm, aerobic environment under controlled conditions". It is truly biological recycling of carbon. By mixing the biodegradable plastic together with other agricultural waste would generate a valuable compost as the main component along with water and carbon dioxide. Thus, the generation of the compost when added to soil would give rise to a more complete natural recycling mechanism as compared to the present context of recycling be it aluminium can or plastic recycling. Furthermore, the value added compost being generated would provide additional incentive to drive the biodegradable plastics venture to success.

• Integration of the material with the various waste management infrastructure

The attributes of biodegradability for a product will only make sense if the product is collected and sent to a waste management facility where the product can undergo biodegradation. In line with the future development of the waste management system, composting, sewage and waste water treatment facilities, anaerobic digesters and active landfills are waste management infrastructures where biodegradability is important. Therefore, to ensure that a product meets today's environment criteria, integration of waste management with the product has to occur and evaluation on the attributes be carried out to determine whether the claim can be validated under such systems.

PRN CONSULT

SPECIAL FEATURE ARTICLE
Review of Lead Toxicity -- Part II*
Razak Hj Lajis, MSc

 Why children and babies are more susceptible to lead poisoning?

Children run the greatest risk being poisoned because lead is easily incorporated into their growing bodies which could disturb the normal growth pattern of cells. Even without direct exposure to environmental lead, unborn child can be affected. A pregnant woman that has been exposed to enough lead tend to have a high lead storage in her bones. The metabolic and physical changes which occur in the body during pregnancy may cause the stored lead to be released into the blood thus exposing the unborn. Lead passes through the placenta easily and fetal blood has almost the same lead concentration as maternal blood. At this critical stage of fetal development, the most likely system to be disrupted is the neurological system of the developing unborn child. Equally as disturbing are the reports that blood concentration of lead in pregnant women of below 25 microgram per deciliter (mcg/dl) can affect early cognitive development in the offspring.

If a woman is exposed to high levels of lead before or while pregnant, the fetus could be harmed. Human milk is low in lead, maternal exposure to lead is however associated with an increased concentration of lead in breast milk. Given that the fetus is even more sensitive to the toxic effects of lead, the maximum acceptable level has been recommended to be not more than 10 mcg/dl.

There is new evidence that lead is harmful at blood levels once thought safe. In 1991, the United States Centers for Disease Control and Prevention (CDC) lowered the amount of lead it considers dangerous in children, from 25 mcg/dl to 10 mcg/dl of blood. Researchers anticipate that as evidence of the low-dose toxicity of lead continues to develop, this definition will be lowered still further. There has been suggestion that the figure is lowered down to 7 mcg/dl. For adults, the Occupational Safety and Health Administration (OSHA) is currently comfortable with a figure of 40 to 50 mcg/dl but with the new development, many reiterated that it is time to re-think the OSHA standard again.

Children can be exposed to lead from eating lead-based paint chips or playing in contaminated soil or environment. Young children are most widely exposed group due to their 'hand-to-mouth' attitude since they tend to put almost anything into their mouth. Some small children seem to possess an abnormal craving for placing unnatural, non-food substances in their mouth. This unusual habit is referred as 'pica'. Lead contaminated items could be easily picked up and swallowed this way.

Children absorb a higher percentage of ingested lead than adults do. When an adult eat lead, the body absorbs approximately 5-15 percent of the ingested metal, slowly excreting the rest. In the child, oral absorption is greater and it can go as high as 50 percent if the children have nutritional deficiencies of other divalent metals such as calcium, iron and zinc. Iron deficiency most notably can increase the absorption of lead several folds. Absorption is also increased in pregnancy and fetal transfer is rapid. Lead absorption from the gut is increased by fasting as well as by chronic deficiencies of any essential mineral, of protein and most vitamins. As the phenomena are more likely to occur in children than in adults, undue lead absorption is of greater concern in children.

Lead dusts that settle on the carpets, floors, furnitures, toys and other objects as well as the hand of the children are most detrimental towards children. As the children are most confined to the house compound, they are most susceptible to lead exposure. Additional lead sources may also come from other activities especially when conducted in the home. These may include pottery and ceramic glazing and re-painting activities. A lot of precaution must also be placed on the removal of lead-based paint from older houses during renovation.

Comparatively, lead concentration in urban soil and air is often much higher than in rural areas. In more polluted areas where lead content of dust is much higher, it is often associated with a significant elevation in children's blood lead levels. In this situation, accumulation of smaller amount of lead for a long period of time in child's body may result in damage that does not become visible until the child is old enough to express learning abilities.

Most of the absorbed lead is stored in the child's bones, with smaller amounts in the bone marrow, soft tissues and red blood cells. Lead accumulation can always occur and eventually reach a toxic level. The half-life of circulating blood lead is approximately one month in normal subjects and that of lead in bone is 20 years. If the condition persists and not corrected, the toxic lead level in the child's body can lead to serious complications including mental retardation. Lead poisoning in children in particular, causes most damage to the brain, nerves, red blood cells and digestive system.

Low-level lead exposure and the IQ of children

The neurotoxic properties of lead at high doses have been recognized for at least a century and are not a matter of dispute. As early as 1940s, an idea was put forward to suggest that childhood exposure to doses of lead insufficient to produce clinical encephalopathy was associated with deficits in psychological function. Children who are lead-poisoned can suffer from damage of the brain and nervous system that may cause behavioral and learning problem. It may also retard physical development of the children. Since these immediate effects of exposure to high lead are well-documented, the interest is now on the long-term effects of low concentration of lead. Others may underestimate the hidden effect of this pervasive environmental hazard. However, there is rising concern about low lead level in children.

Latest scientific finding showed that relatively low-level lead exposure in children can result in delay learning, impaired hearing, growth deficits and behavioral defects. Thus when a child is exposed to the same amount of lead as that exposed to an adult, the potential damage is greater. Recent work has documented a relationship between blood lead levels in children with a slight decrease in IQ. The level described to be as low as 10 mcg/dl. Impairment of cognitive function on a progressive decrease in IQ has also been demonstrated with increasing blood lead levels.

Lower levels of lead exposure are now recognised as being associated with altered neuropsychological function, decreased intelligence and performance. Experimental evidence has shown that children's risk of development problems is at blood levels of 10 to 15 mcg/dl and possibly lower. In neonates, lead levels greater than 10 mcg/dl in the cord blood are associated with slow development. Lower blood lead levels also impair haem synthesis and cause other biochemical changes, such as reduced vitamin D levels.

The table below briefly describes some of the clinical effects of various concentration of blood lead levels.
 

How to know if one has been exposed to lead?

Blood tests are available to measure the amount of lead in the blood and thus estimate the amount of one's exposure to lead. Blood tests are commonly used to screen children for potential chronic lead poisoning. The principal tests for detecting lead toxicity are blood lead levels (BLL) and free erythrocyte protophyrin (FEP) levels. Other dignostic laboratory tests for lead poisoning include urinary delta-ALA, urinary coproporphyrins and blood smear. As for FEP, it is less useful for screening lead concentration less than 25 mcg/dl as the erythrocyte protoporphyrin level usually does not rise if blood lead levels are below this concentration. With the evidence that blood lead levels as low as 10-15 mcg/dl may be toxic, its positive predictive value is limited. However, it is a sensitive test for concentrations above this level. CDC considers children to have an elevated level of lead if the amount in the blood is at least 10mcg/dl.

In suspected lead poisoning, with acute symptoms, the diagnosis must be confirmed with haste. The BLL and FEP levels should be obtained. The BLL is accurate, reproducible and reasonably precise. Despite being the more accurate test, blood lead determination is still subjected to contamination with environmental lead especially when collecting finger-stick specimens. Thus venipuncture specimen is very much preferred. Blood lead level is generally performed as a confirmatory test in persons with an elevated FEP. This is necessary because standing on its own, FEP test is not so confirmative since iron deficiency can also give this result. If the BLL and FEP levels are not available for rapid confirmation of the diagnosis, examination of the blood smear for stippling and other diagnostic tests available can be done. Other supplementary blood tests may include hemoglobin content, hematocrit level, red blood cell count and indices, bilirubin level and total iron-binding capacity. Lead in teeth and bones can be measured with X-rays, but this test is not as readily available.

What and when are treatment and medical intervention necessary?

Medical intervention should begin with thorough clinical examination, diagnostic studies of lead toxicity and when indicated, a lead mobilization test. When the test results are elevated, the blood lead concentration needs to be re-determined. Once a diagnosis of increased lead absorption has been confirmed by venous blood lead determination, the main mode of intervention is prompt and complete termination of any further exposure to lead is necessary.

This intervention requires accurate identification of the source of lead. The source must either be removed or the victim taken away from the unsafe environment. Other treatment modalities include improving nutrition and chelation therapy. The lead mobilization test may be used to assess the pool of lead in a child for whom chelation therapy is contemplated. It is determined by measuring lead diuresis in a timed urine collection following a single dose of chelating agent.

Treatment of lead poisoning by chelation therapy depends on the treatment management and the likelihood that the chelation will cause a rapid drop in total body burden and no significant side-effects are experienced by the patient. Because chelating agents are potentially nephrotoxic, BUN or serum creatinine values should be determined before chelation therapy to rule out occult renal disease. Routine urinalysis might be considered.

There are currently a number of chelating agents used for the chelation of lead. Among chelators of choice are dimecarpol (BAL - British Anti Lewisite), calcium disodium ethylene-diaminetetraacetic acid (CaNa2-EDTA or EDTA), dimercatosuccinic acid (succimer or DMSA) and d-penicillamine. All the chelators act by mobilizing lead from various sites in the body. Therefore the effective use of these agents requires fully understanding of their actions, effects and side-effects.

Chelation with EDTA has been widely used as a treatment for lead poisoning after it was shown to alleviate clinical signs of poisoning. It has a high affinity for lead. EDTA has been demostrated to decrease blood lead concentrations, reverse hematologic effects of lead and increase the excretion of lead in urine. EDTA removes lead from the extracellular compartment and increase urinary excretion of lead by many folds. By depleting the extracellular compartment, it draws lead from the soft tissues, CNS, and red blood cells thereby reducing lead in these areas.

It is recommended that all severely affected children be treated with both EDTA and BAL for specific number of days as to minimize the toxic effects and accelerate urinary excretion of lead. It was noted that a more rapid decline in blood lead concentration during chelation when BAL was added to EDTA. Nephrotoxicity may develop in patients treated with a combination of dimercaprol and EDTA. A smaller percentage of patients may experience acute renal failure. Therefore an appropriate fluid therapy and monitoring of urine output and renal function are essential with the use of EDTA.

BAL acts to chelate lead both intra- and extracellularly. The chelated complexes are excreted in the bile and urine. Unlike EDTA, it chelates lead from the brain. Because of this, dimercaprol is commonly combined with EDTA when lead encephalopathy is present. BAL itself may be toxic. The toxic effects are usually mild and transient which may include febrile reactions, nausea, vomiting, headache, conjunctivitis, rhinorrhea and salivation. BAL may also induce hemolysis to the G-6-PD deficient individual.

A course of EDTA and BAL or EDTA alone may be follow by oral chelating agents, succimer or d-penicillamine. The main objective of oral chelation therapy is to reduce the body burden so that blood lead does not rebound to unacceptable levels. They are effective by mouth whereas the other two chelating agents (BAL and EDTA) are not. Having a closed resemblance to penicillin, the toxicity of D-penicillamine mimics that of penicillin sensitivity: fever, rashes, leukopenia, hemolytic anemia and Stevens-Johnson syndrome. Anorexia, nausea and vomiting may also occur with administration.

As for succimer, a water-soluble analog of BAL, adverse reactions are manifested in term of mild gastrointestinal symptoms, general malaise, transient elevation of liver enzymes, a decrease in hemoglobin level and hypersensitivity. Unlike BAL, succimer has not caused hemolysis to a number of patients with G-6PD deficiency receiving the therapy.

CDC has come out with a statement which call for children to be referred for medical at 20 mcg/dl or higher. Residential clean-up and vitamin and mineral supplementations are recommended as intervention and prevention programmes to those who have lower blood lead levels (see below).

Class of child based on blood lead levels (BLL) 

 Adapted from CDC, Preventing Lead Poisoning in Young Children. A statement by the Centers for Disease Control and Prevention, October 1991, US.

What are some intervention and prevention programmes available?

The issues of lead removal from the environment is indeed a tricky one. The removal process may end up as a political, economical as well as a medical one. As we all know, much of the lead in the atmosphere come mainly from automobile emissions and industrial wastes. Thus any type of legislation to stop manufacturing or using leaded gasoline may provoke an outcry of anger and protest from the users of leaded gasoline. Loss of engine efficacy, increased valve wear and additional cost of engine lubricants and additives are some common grouses being brought up by customers.

Efforts must be focussed initially on children with lead poisoning severe enough to require medical intervention (greater than 20 mcg/dl). A suitable strategy could later be drawn up to include children with lower blood lead concentration (less than 20mcg/dl). Even blood lead levels that are not high enough to warrant medical treament may require action to reduce the environmental source of lead. To begin with, there could be an increased screening of children for elevated blood lead levels especially in high-risk areas, together with community prevention programmes. In addition, a continuous reduction of children's exposure to various identifiable sources of lead in the environment must be planned.

A national strategy may be required to develop guidelines for health professionals, public and federal agencies on lead hazard identification and childhood lead poisoning prevention programmes. This may include education of the public, the medical profession and industry as to the hazards of lead toxicity.

In general, a concerted effort in environmental monitoring and medical surveillance can result in substantial reduction of lead exposure among populations who are at risk.

One thing for sure. We can never practically condoned our child to be exposed to the environment. Ignorance and complacent often spell disaster and tragedy. Ignorance of personal hygiene practices resulted in secondary contamination. Thus it is better to be well-informed about it rather than to have one's mind doggedly closed to it.

A list of environmental ills caused by plastics includes:

• Workers in (and people living near) petroleum refineries and some type of plastic resin factories run an increased risk of getting various kinds of cancer.
• Fires in homes and commercial buildings kill nearly 5,000 Americans each year, many of them because of the toxic smoke created by burning plastics. This hazard, unique to plastics, has been consistently played down by the plastics industry (and by those who regulate such matters) since it first appeared in the 1960s.
• More than a million seabirds and approximately 100,000 sea mammals die each year after ingesting, or becoming entangled in, plastic, debris. Less deadly, but economically damaging to the tourist industry is plastic litter on beaches. One 3-hour cleanup of a 157-mile stretch of beach in Texas in 1987 collected 31,773 plastic bags, 30,295 plastic bottles, 15,631 plastic six-pack rings, 28,540 plastic lids, 1914 disposable diapers, 1,040 tampon applicators, and 7,460 milk jugs.
• A significant percentage of municipal solid waste is plastics: 7% of garbage by weight, and 18% to 30% by volume, is plastics, which physically disintegrate very slowly. In an incinerator, burning plastic releases hydrochloric acid which degrades the incinerator rapidly, releases chlorine which is then available to form dioxins, and releases toxic metals that were added to the plastics to give them color or stiffness or some other desirable characteristic.

Classification of Plastics

There are almost 50 different kinds of plastics used in the production of everyday items that we used eventually dispose off. Of these fifty, six are used extensively enough to be classified as main plastics with the remaining grouped into a seventh category. The plastics industry has devised a cording system for the seven categories which is usually used to mark the appropriate type of plastic. Those coding is known as the recycling code for polymers. 

1. PET (Poly Ethylene Terephthalate)

2. HDPE (High Density Polyethylene)

3. PVC or V (Vinyl polyvinyl chloride)

4. LDPE (Low Density Polyethylene)

5. PP (Poly propylene)

6. PS (Polystyrene)

7. All other plastics and multiresin plastics

PET
Accounts of 20 - 30% of the bottle market and also is the most commonly recycled plastic in the US. PET formed in a variety of food stuff package and is used mainly for its clarity, toughiness and ability to resist permeation by carbon dioxide. Some examples of products possible from recycled PET are carpets, auto parts and geotextiles.

HDPE
Accounts for 50 - 60% of the bottle market. HDPE is used to make milk jugs, butter tubs, detergent bottles, motor oil containers and bleach bottle to name a few. Recycled HDPE can be used to make flowerpots, trash cans, traffic borders, industrial pallets and other related items.

PVC
Accounts for 5 - 10% of all plastic packaging. It is used to make bottles (water, shampoo, cooking oil), garden hoses, flooring, credit cards, shower curtains and many more related items. The main problem with PVCs is that when it is incinerated it contributes to the production of HCl. Recycled PVC is used to make drainage pipes, handrails and sewer pipes among others.

LDPE
Accounts for 5 - 10% of all plastic produced. Its uses include shrink wrap packaging, plastic sandwich bag, and clothing wrap. Recycled LDPE can be used to make almost everything that the virgin resin is used for.

PP
Accounts for 5 - 10% of all plastic produced. It is used to make plastic bottle caps, plastic lids, drinking straws, broom fibers, rope, twine, yogurt containers and carpets. Recycled PP can be used to produce or has the potential to be used for auto parts, bird feeders and battery cases.

PS
Accounts of 5 - 10% of all plastic produced. It is used to make stryroform cups, egg cartons and fast food packing. Recycled PS can be used to make light switch plates, note pad holders, cassette tape cases, reusable cafeteria trays and waste baskets.

Others
Account for 5 - 10% of all plastic produced. There are frequently found as composite plastics. These plastics are high performance plastics. Recycling is often limited because of the inability to blend the plastics. Their uses may be for landscaping lumber and picnic benches.