ON November 5, 2016 the Pomona municipal dumpsite of Harare started burning again. Satellite images, show the smoke plume caused by the Pomona fires (Figure 1), that have become a regular phenomenon. While the Pomona dumpsite is one big annual burning event, residents of Harare are in the habit of burning their household garbage — plastic bags, old cellphones, etc – in their backyards or even on the roadside as garbage collection appears to be sporadic.
Garbage burning has been used many a time in trying to control mounds of garbage that accumulate over a period and where other forms of disposal seem not to be addressed.
However, such burning has negative impacts on the environment and all living species, especially the human species.
We know when fire burns, a lot of smoke is emitted.
We know this smoke becomes part of the air we breathe. The question is “Do we want to breathe smoke? What is the effect of that smoke to our health?” We might be able to endure smoke of burning wood, but what about burning plastic bags, an old cellphone or even an old tyre, etc?
What happens when plastic burns?
What gets released into the air? What effect does it have on the health if we breathe it?
Plastic creates toxic pollution at every stage of its existence: manufacture, use and disposal. Every bit of plastic that has ever been created still exists. Even if plastic gets incinerated (a form of controlled burning) its poisonous compounds still exist as particulate matter, and can escape as toxic matter into the atmosphere.
Let us just imagine what happens at this dumpsite where the burning is uncontrolled! Some major compounds in plastics include vinyl chloride (in PVC), benzene (in polystyrene), phthalates and plasticisers, Bis Phenol-A (BPA) and formaldehyde.
The additives used during the manufacture of plastics that give the polymers their end use properties are varied. It is these additives that form toxic chemicals that are expelled into the environment when the plastics are burnt.
These toxic chemicals have adverse effects on animals and human beings. For example, the BPA is reported to affect the endocrine system. Endocrine system is the hub of human control and BPA has an estrogenic side effect. This side effect leads to premature birth, intrauterine growth retardation, preeclampsia and stillbirth. BPA has also been shown to lead insulin resistance and diabetes.
Some plastic monomers have been linked to cancer. The harmful effects of the chemicals have been found pronounced in new-born babies as the toxins pass through the placenta during pregnancy. Phthalates have been found to deposit in the fatty tissues of the body and cause disorders like male reproductive dysfunction, breast growth and testicular cancers.
e–Waste
Electronic-waste (e-waste) refers to end-of-life electronic products including computers, printers, photocopy machines, television sets, mobile phones and toys, which are made of sophisticated blends of plastics, metals, among other materials.
Just like plastics, it has been shown that incomplete combustion of e-waste and of processed materials is a source of various toxic chemicals. This means by uncontrolled recycling of e-waste, i.e. by heating and burning it, toxic metals (such as lead [Pb]) as well as persistent organic pollutants (POPs, such as dioxins/furans [PCDD/Fs], and flame retardants [PBDEs]) are released into the environment, which may affect human health either directly or indirectly.
For example, the recovery of copper wires through the burning of polyvinyl chloride (PVC) and PBDE protected cables can release toxic chlorinated and brominated dioxins (PCDD/PBDD) and furans (PCDF/PBDF), and the open burning of computer casings and circuit boards stripped of metal parts can produce toxic fumes and ashes containing polycyclic aromatic hydrocarbons (PAHs).
Due to its wide historical use as coolants and lubricants in transformers and capacitors, and as hydraulic and heat exchange fluids, polychlorinated biphenyls (PCBs) are also expected to be present in the e-waste stream.
Therefore, high concentrations of POPs and heavy metals/metalloid are detected in the air near sites where e-wastes (e.g. plastic chips, wire insulations, PVC materials and metal scraps) are incompletely combusted.
Effects on humans
The burden of ill-health caused by particulate pollution, either on its own or in combination with gaseous pollutants, is enormous. In 2012, 3,7 million premature deaths were attributable to ambient air pollution. The increase in daily mortality shows that on a global scale, 4 percent to 8 percent of premature deaths are due to exposure to particulate matter in the ambient and indoor environment (WHO, 2000).
Airborne pollutants affect health in varying degrees of severity, ranging from serious illness to premature death in extreme cases. Such pollutants may produce immediate (acute), as well as long-term (chronic), symptoms. Air pollution causes serious health problems, even when the levels are much lower than WHO limits (WHO, 2000). Exposure to particulate matter can aggravate chronic respiratory and cardiovascular diseases, alter host defences, damage lung tissue, lead to premature death, and possibly contribute to cancer.
That means that in Harare, where we burn municipal waste in open fires, it is no surprise that under such high concentrations of toxic chemicals, the municipal workers, dumpsite scavengers and local residents (especially mothers, infants, children, the elderly and the immune compromised) will be adversely affected through inhalation, dermal exposure and oral ingestion of contaminated drinking water and food.
As the economy will grow in Zimbabwe and more people consume plastics and electronic goods, it is expected that a substantial quantity of waste will find its way to the waste dumps, and we have to ensure that these are not burned, either by mistake, or intentionally.
Siting of Dumpsites
The Pomona dumpsite is situated just north of Mt Pleasant and Vainona in Harare and it is surrounded by residential areas, a recreational golf course and agricultural land, in addition to other places where people go to work.
From historical weather records in Harare the predominant wind direction is east-north-east and blowing towards the west-south-west (Figure 3). That means, in case of a fire at the Pomona municipal waste dump the toxic smoke will most likely be blown towards the residential areas of the City of Harare and beyond. According to reports this was the case during the previous fires at the Pomona dump.
In all the fire events’ satellite images reveal that the smoke plume travels all the way past the city centre, over the high-density residences, including Mbare, Glen View and Dzivarasekwa, all the way to Beatrice, Chegutu and Kadoma (Figure 2).
This was mapped using the satellite image observations of October 20 2013, as well as November 6 and 7, 2016 and relating it to the geographic layout of the city. Therefore, more than half of the residents of the city were actually exposed to the poisonous smoke of the fire at the Pomona dumpsite. This also means that if the municipal waste dump of Harare remains at the Pomona site these areas of the city are exposed to the health threats mentioned above, whenever the Pomona dump will burn again, or continues to burn.
Combustion and thermal processes are dominant sources of air pollution and they also produce chronically toxic products during incomplete combustion. To safeguard ourselves, we in Zimbabwe have to prevent uncontrolled fires of any waste! As there is currently no safe way to dispose of plastic waste and burning plastic is a great health hazard, we need to improve the current solid waste management system in Harare and at its dumpsites.
Remedies
Broadly, two classes of presumptive remedies exist to deal with abandoned and uncontrolled waste sites: containment and treatment. Containment simply prevents the spread of contaminants to the soil, air, and water, whereas treatment employs technologies to rid the area of contaminants.
Containment is enforced by the Environmental Management Agency through the requirement of lining waste dumps. This involves the construction of an impermeable containment layer at the bottom of the dump-site and therefore gets implemented on new sites, before the dumping starts, after which the waste also has to be covered regularly.
As opposed to containment, the treatment regimens for solid wastes most often employed are some form of combustion or thermal treatment, including a) incineration, which uses high temperatures to degrade contaminants; b) on-site thermal destruction, which is, in effect, a low-grade incineration process; and c) thermal desorption, in which toxic chemicals are first desorbed from the medium, collected, transported off-site, and then usually incinerated.
Where to site municipal dumps has to be carefully considered, so that the dumpsites are located downwind of settlements and farming area. They have to be secured, covered and fire has to be prevented. The dumpsites should be fenced so that only authorised persons can enter the sites. There should be fire prevention mechanisms implemented and fire extinguishing equipment and teams on standby.
Furthermore, recommend alternative methods of waste management are known, and, local municipalities should properly dispose of poisonous waste, which includes plastics and e-waste by first of all separating it from ordinary trash.
In order to safeguard population and the environment, we have to stop burning our waste in open fires. Policy-makers should work towards a world free of plastic pollution and its toxic impacts on humans, animals and the environment.
Companies that have solid waste from their products should be held accountable or responsible for recovering and recycling their product after it is used. A good example of how this works is the case of drinks bottled in glass: where the glass bottles are being received back by the beverage manufacturers from the customers and reused, hence, hardly any glass bottles are found in the environment in Zimbabwe.
Also, companies should rather use recyclable plastics that can be changed into other useful products by a method called Pyrolysis which is the breaking down of the macromolecules into shorter chains. These are high-density polyethylene (HDPE), polyethylene (PE) and polypropylene (PP), to mention just a few. These recyclable plastics can be recycled to make diesel, kerosene (paraffin), petrol and wax if the heat application is controlled. As part of their corporate social responsibility (CSR), companies could be urged to work together in establishing recycling plants depending on the type of waste their products produce.
Research into biodegradable plastics would be another way to minimise plastic pollution. SIRDC has this as one of the potential areas of their project research. Biodegradable plastics hold promise, but are not currently a perfect solution as they are more expensive to produce, and many use plant resources such as maize or molasses thus creating competition for food supply. Strategies would have to be put in place to balance the need for durable plastics in some applications, and biodegradable compounds in others.
This information note was compiled by the Environmental Sciences (ESI) and the Geo- Information and Remote Sensing (GRSI) Institutes of the Scientific and Industrial Research and Development Centre (SIRDC). Email: [email protected]