Asbestos Cement Waterpipes: A Health Hazard?

Introduction

Asbestos is a generic term covering a range of naturally occurring fibrous silicate minerals. It consists of six unique minerals — chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite — belonging to the serpentine and amphibole families[1]. Chrysotile (white asbestos) is the major type used in manufacture of asbestos products.

Asbestos has been known to humans for over 4500 years. Its commercialisation began in the mid-19^th century. Because of its remarkable durability, fire resistance, abundance and inexpensive nature, it was hailed as a wonder product.[2] Exploitation and application in huge quantities ensued. Asbestos applications include roofs, ceilings, walls and floors in the home and business environments, as well as asbestos cement (AC) pipes and automobile brake linings, gaskets and boiler seals, and insulation for pipes and flues for heating appliances.

However, in the 1930s, the hazards of asbestos began to be understood and the dust from it turned out to be a leading occupational health problem of the 20^th and 21^th centuries. Studies revealed asbestos to be a significant occupational carcinogen. Epidemiological statistics suggest that globally about 90 000 people die each year from asbestos related diseases.[3] In South Africa, according to the Department of Environmental Affairs, about 200 mesothelioma cases are reported yearly[4].

As a result, the World Health Organization (WHO), the International Labour Organization and the United Nations Environment Programme, called on countries to eliminate asbestos-related diseases by ceasing to use asbestos products.

Many countries have adopted national asbestos bans, but others continue to use asbestos[5]. South Africa banned asbestos use in March 2008. The importation, exportation, exploitation, as well as the use and manufacturing of asbestos have been prohibited since then. But the legacy of asbestos lives on. This is because it remains in buildings as a fireproof material. It is often found in insulation, floor tiles, joint compound and other components of homes and other buildings, [6] threatening lives.

AC pipes have been installed in water reticulation systems by many municipalities throughout the country over many years. This review explores whether the continued use of AC pipes in the water reticulation systems pose any known risks to human health.

Asbestos Cement Pipes

Asbestos was first used in plumbing in 1931. The mineral’s fibres were mixed with concrete slurry to make a tube that was structurally sound. This material was called asbestos cement. By the early 1950’s, these concrete tubes were commonly used in the drinking water distribution networks across cities in many parts of the world.

AC pipes contain varying proportions of asbestos fibre, cement and other materials. These include quartz-containing mainly silicon oxide and free lime. Most AC pipes contain between 15 and 20% asbestos fibres [7].

Asbestos Cement Pipe Replacement Project in South Africa

Most of South Africa’s pipelines in the water distribution networks were installed in the early 1950’s and 1960’s. These pipelines are mostly made of cement, asbestos or steel. As noted by the Southern African Stainless-Steel Development Association (SASSDA) the exact makeup of the water pipelines in the country is not known. Available evidence suggests that cast iron pipes were used from 1870-1930; cement-lined cast iron from 1930-70; asbestos cement from 1950-70; ductile iron pipes from 1960, and polyvinyl chloride from 1970 onwards. [8]

AC pipes are still used in potable water distribution by many municipalities in South Africa. What is more worrying is that most of the AC pressure pipes in use have passed their design/service life. This led the Southern African Plastic Pipe Manufacturers Association (SAPPAMA) in 2013 to issue a strong warning pointing out that because the pipes were installed over fifty years ago, they were corroded.[9] As a result, there have been frequent pipe bursts. The principal observed impact is on service delivery and increased maintenance costs, as well as water losses. But it has an additional risk: the potential to increase asbestos fibre concentrations in potable water.

AC pipes are among the leading sources of asbestos fibres in drinking water. Aggressive water pressure, length of pipes and age are the major contributory factors for the exfoliation and the subsequent release of asbestos fibres into drinking water. In addition, elevated asbestos fibres have been reported in drinking water during installation and repairs.

This risk has led many water service authorities to introduce AC pipe replacement projects. These include replacement projects in Tshwane, Polokwane, eThekwini, Knysna and Lesedi. Nonetheless, in some the AC pipes are still in use without any set timelines for replacement (e.g. Prince Albert, in the Western Cape).[10]

Sources of Asbestos in Drinking Water

In the water supply chain, asbestos can be introduced at two stages:

1. Pre-treatment: Asbestos may be introduced into water by the dissolution of asbestos-containing minerals and ores (geologic erosion) as well as from industrial effluents and atmospheric pollution. However, water filtration processes, when operated properly, have been shown to substantially reduce asbestos fibre concentrations in drinking water.[11] For instance, diatomaceous earth filtration can remove both amphibole and chrysotile fibres, with demonstrated removals as high as 99.99%.[12]
2. Post-treatment: the use of AC pipes is associated with the release of asbestos fibres into drinking water at post water treatment phase. This is a major concern because fibres released post treatment are not eliminated at all. They therefore end up in the distribution points. The amount of asbestos introduced into the distribution system depends on various factors.
   1. Age: The service life expectancy of AC is estimated to be roughly 50 years. While the Chrysotile Institute estimates AC pipe lifespan at 70 years, actual service life depends on pipe condition and working environment.[13] The service life expectancy of most AC pipes depends on many factors such as construction methods, quality of pipe manufacturing, soil corrosivity and water chemistry.[14]
   2. Aggressiveness of water supply: High water flows in the distribution system can lead to the erosion of AC pipes walls. This results in elevation of asbestos fibre counts in water. High flows caused by flushing or firefighting can stir up sediment in AC mains. If this occurs in generally low-flow areas, fibre counts can rise to 10 or even 100 times typical values (Logsdon,1983).
   3. Distribution system operation and maintenance procedures: Unless the pipes are flushed out under pressure, drilling and tapping of AC pipes can introduce and elevate asbestos containing debris into distribution systems.

Pulmonary and Non-Pulmonary Risks of Asbestos Exposure

Adverse pulmonary effects of asbestos have been well documented. This takes place mainly through on-the-job inhalation of airborne asbestos fibres (occupational exposures). For instance, it has been well established that, after a long latency period (about 30 years)[15] inhaling significant quantities of airborne asbestos leads to (i) asbestosis (scarring of lung tissue), (ii) mesothelioma (malignant tumours, cancers that develop around the lungs), (iii) pleural plaques (thickening of membranes around the lungs) and (iv) other forms of lung cancer.

According to Boulanger et al.[16] asbestos diseases have manifested three distinct epidemiological waves. First, among miners; secondly among workers in the asbestos manufacturing industry; and, thirdly, secondary occupants of asbestos-infiltrated buildings.

A fourth “wave” could usefully be added. This is exposure via non-pulmonary routes, including ingestion. What remains disputed, however, is whether non-pulmonary exposures to asbestos fibres could lead to adverse health impacts. Some studies suggest that evidence linking non-pulmonary exposure to asbestos fibres, albeit suggestive, is not conclusive (Kim et al., 2013).

However, the WHO has repeatedly (e.g. in 1996, 2003, 2012 and 2014)[17] disputed that ingestion of asbestos through drinking water creates potential health risks. This led WHO to exclude asbestos from its priority list of waterborne pollutants. It has not proposed drinking water quality criteria for asbestos.Nonetheless, asbestos has been kept on the WHO watchlist and it does not recommend the use of asbestos containing pipes.

But studies have disputed the WHO’s position on asbestos hazards in drinking water. Claula & Genaro [18] for instance state that health hazards might also manifest after ingestion, including drinking asbestos fibre contaminated water over a long period of time (Andersen et al. 1993;Germani et al.1999; Kjaerheim et al. 2005; Bunderson-Schelvan, 2011; Boulanger et al. 2015).

The studies have linked asbestos exposure through ingestion with adverse health outcomes. These include gastrointestinal tract-related cancers including of the stomach[19]^;[20], colorectal and genital malignancies [21] and oesophageal cancers.[22]

While some uncertainty remains as to whether ingesting asbestos fibres is hazardous to human health, precautionary approach does not require certainty for beneficial actions to be taken. The Precautionary Principle (PP) entails a strategy for approaching issues of potential harm when extensive scientific knowledge on a matter is lacking or there are existing scientific uncertainties. [23]^;[24]In accordance with the PP it is advisable that when an activity raises threats of harm to human health or the environment, precautionary measures should be taken even when some cause-and-effect relationships are not fully established scientifically. [25] From this it is suggested that municipalities that still use AC pipes in drinking water distribution systems should imperatively replace them as a precautionary measure.

Conclusions and Recommendations

Asbestos remains a leading occupational health concern. It is a well-known pulmonary carcinogen mostly spread through inhalation of fibres. Yet epidemiological studies are linking exposure to asbestos via non-pulmonary routes (i.e. ingestion). Consensus has not yet been reached as to whether observed non-pulmonary cancers can be exclusively linked to ingestion of asbestos fibre. The epidemiological evidence to date is suggestive but not conclusive. Nevertheless, non-pulmonary ingestion of asbestos fibres is counter-indicated.

While these debates and scientific explorations are underway, millions of South Africans are exposed to non-occupational sources of asbestos fibres. Through drinking water that is supplied by aged and deteriorating asbestos cement pipes.

The present state of the evidence indicates that municipalities still using AC pipes should replace them as a matter of urgency. This suggests that a national asbestos-in-potable water audit is urgently desirable. This is because the exact makeup of the water pipelines in the country is not known and asbestos is not routinely monitored in South African drinking water. The audit should:

1. List all municipalities that are still using AC pipes in water reticulation networks, indicating when the pipes were installed as well as intended replacement timelines.
2. Conduct composite sampling and laboratory analyses of drinking water distributed via AC pipes. These should target pipe burst, repairs and tapping effects.

Nhlanhla Mnisi
Researcher
nhlanhla@hsf.org.za

[1] URL: https://www.asbestos.com/asbestos/types/