16 July 1993 Hazardous Wastes: How can they be managed? Do they endanger our health?

Appropriate legislation and open communication between industry, local and national governments, and the public are of major importance in risk assessment and the proper management of hazardous waste material, says Dr Ravi Gooneratne, a Lincoln University toxicologist who has just returned from the first International Conference on "Health effects of hazardous waste", held in Atlanta, Georgia, USA.

Thousands of tonnes of hazardous waste chemicals are produced every year in New Zealand. There are an estimated 7800 contaminated sites in New Zealand, including 1580 sites that may be at high risk. It is, therefore, not surprising that many questions are being asked about the potential environmental hazards of such wastes at both industrial and landfill sites in New Zealand. There is a major difference of opinion on whether or not waste sites represent a serious health threat to those living near sites. Whether a public health risk exists will depend on the amount of direct exposure, groundwater contamination and toxic gas migration which actually occurs.

What are hazardous wastes?

Hazardous wastes are a by-product of industry. How we deal with them, dispose of them and prevent them are the key to the quality of the air, the environment and our health. All industries produce wastes as leftovers from manufacturing processes. Items we use in our everyday lives such as medicines, fabrics, furniture and machinery are all manufactured by processes that generate waste materials much of which is harmless but some may be hazardous.  A waste is a hazard if it has some or all of the following features:

• is flammable - easily able to ignite or catch fire;
• is corrosive - able to damage containers  or other materials  (including human tissue) on contact;
• is reactive - likely  to  explode  or  catch  fire  when  contacting  water  or  other materials;
• is toxic - causing illness or death when one is exposed to certain amounts;
• is radioactive - gives off harmful radiation; and
• is harmful to living organisms by building up in the body.

Hazardous wastes are recognized as a major environmental and social problem of the 1990s. The proper disposal of hazardous wastes is a real issue. Although the problem has only recently captured public attention, it's the result of decades of inappropriate waste disposal. A major cause of the waste problem is the demand for consumer products at the lowest short-term market cost. This philosophy frequently results in the generation of large quantities of dangerous by-products. We cannot power automobiles, paint houses, grow food, make and dye clothes or print books without generating substantial amounts of hazardous wastes. Technology is progressing more rapidly than our ability to deal with the wastes we produce.

Waste Management

In the past most waste has been poured into landfill sites. Many of these sites did not have a lining to prevent seepage of substances into the soil. Many wastes can move through the environment contaminating soil, water and air.

In the USA, industry is required to keep "cradle to grave" records of waste.  This means a company must record the waste production (the cradle) and where and how it is stored or shipped. The final disposal of waste (the grave) must also be recorded. Such record keeping helps to ensure that waste is disposed of properly and not dumped illegally. Knowing where, and in what volumes hazardous wastes are located in any given site is extremely helpful for fire fighters, emergency personnel and the environmental spill response teams.

In future, companies in New Zealand that discharge wastes into the air, waterways and sewer systems will be required to have permits. Most of the hazardous waste from industries will have to be managed on site with only a negligible amount allowed to be transported to off-site treatment and disposal facilities.

Hazardous waste management technology includes five major overlapping categories: recovery and re-use; pre-treatment; deepwell injection; incineration (burning); and landfill or burial. The ideal solution is to eliminate or reduce the amount of waste generated. However, only limited changes can be economically made to existing facilities in the pursuit of this goal. The recovery and re-use of commercially valuable materials from hazardous industrial waste is therefore the preferred disposal method. Many substances can be recovered and then re-used for another process, or piped or transported to another industry which may need this material.

Hazardous waste should be pre-treated to detoxify (make it safe) prior to subsequent disposal. With some pre-treatment methods wastes are so completely detoxified they need no further treatment or monitoring. Although not common in New Zealand, deep well injection is another method of disposal of wastes. Liquid waste is pumped and drained through injection tubes into porous rock formations. Incineration is probably the safest and most effective method of disposal of most types of hazardous waste but may involve complex and costly technology and expensive anti-pollution devices. In New Zealand, burial in 'secure' landfills is still an option for waste disposal. These 'secure' landfills are not the same as municipal sanitary landfills, which take domestic garbage. Rather they have impermeable liners which prevent contamination of surface and groundwater. Can any landfill, however ideally constructed and monitored, ever be truly 'secure', except for a short term? Opponents of landfill suggest that, sooner or later, toxins will leak, escape and contaminate surrounding soil and water sources.

Although there will be regulations regarding specific treatment and disposal of different types of hazardous waste in the "new" Hazardous Wastes Bill currently before Parliament, the experience of other countries suggests there is bound to be frequent regulation violations, accidents, and leakages that would enable toxic wastes to enter the environment and contaminate air, water, soil and food and cause harm.

Health Hazards

United States Environmental Protection Agency (EPA) has made a list of the environmental and health effects of poor waste management. These include ground water contamination, forced closure of wells, habitat destruction, soil contamination, fish kills, livestock losses, inoperable sewage systems, damage to crops and wildlife, air pollution, explosion of chemicals at abandoned sites, and human health problems.

The possible health effects from exposure to toxic chemicals from waste sites vary, and depend on how much (dose) and how often a person is exposed to the chemical. Chemicals are known to cause acute (one time exposure to a large dose) or chronic (repeated exposure to small doses) effects.  Usually hazardous wastes cause chronic effects which can result in either short and/or long term health effects. Short term effects are mostly due to irritation at the site of contact (which can result in watery eyes, runny nose, skin damage) and mild depression of the nervous system. These effects may disappear with time. Long term effects are far more serious and include damage to many internal organs such as the liver, kidney, thyroid gland, lung and cancers in these organs, and nasty effects on the blood and immune systems such as leukaemia. Recognizing these as public health problems was an important issue discussed at the International Conference on "Health effects of hazardous waste", Atlanta, Georgia, which I attended recently. Little is known about effects on humans of exposure to many of the hazardous substances. Even less is known about the potential effects of exposure to mixtures of chemicals. For example, a common industrial solvent such as benzene may increase the toxic effects of other chemicals. On the other hand, toxicity may be decreased in certain mixtures. For example, toluene (another common industrial solvent) may reduce the toxicity of benzene.

The United States Government has now created a new agency (Agency for Toxic Substances and Diseases Registry - ATSDR) to set up a new scientific database identifying and following up people exposed to chemicals in hazardous waste sites. These records should help researchers and health professionals assess long term effects of exposure to hazardous substances. New Zealand should learn from the experience of industrialized countries such as USA and Germany which have major environmental problems connected with hazardous wastes and take precautionary action.

Summary:

Hazardous waste sites are a threat to New Zealand's clean green image. It's an enormous task to rectify the mistakes of the past. Cleanup of 1580 high risk sites identified so far in New Zealand is estimated to cost $1.6 billion.  Recovery and re-use of waste chemicals must be undertaken or if not possible, ways of containing waste chemicals must be improved and implemented. The Hazardous Wastes Bill introduced to Parliament recently is a step in this direction. This Bill should pave the way for co-ordinated action on serious toxic waste problems. It is not only the legislation but also open communication between the industries, local and national governments, and the public which is essential for proper management and risk assessment of hazardous waste.