Supporting One Health through Environmental Safeguards

Environmental safeguards can help address issues in the livestock sector in developing countries. Photo credit: ADB.


The coronavirus disease (COVID-19) pandemic put the spotlight on the interface between the health of humans, animals, and the environment, and it has rekindled interest in the One Health approach,(link is external) which was initiated in the early 2000s. Under this approach, experts of related disciplines collaborate and share necessary information to address issues like food safety and control of zoonotic diseases.

The Asian Development Bank (ADB) promotes One Health in its proposed Greater Mekong Subregion (GMS) Cross-Border Livestock Health and Value Chains Improvement in Cambodia(link is external) and the Lao People’s Democratic Republic(link is external) (hereafter referred to as GMS projects) to better prepare these countries in preventing and controlling zoonotic diseases that can be transferred from animals to humans and vice versa.

The World Health Organization (WHO) defines environmental health as factors in the environment that affect human health. It also refers to assessment and control of environmental factors, including the direct pathological effects of chemicals, radiation, and some biological agents in the air, water, soil, and food. It aims to prevent diseases and create health-supportive environments. WHO estimates that about 24% of deaths are linked to the environment.

The GMS projects consist of investment subprojects (hardware activities) and policy and capacity building (software activities) as is typical for all ADB projects. Subprojects in Cambodia and the Lao PDR include mainly veterinary vaccine production, quarantine station at border zones, livestock abattoirs, breeding centers with liquid nitrogen production for semen storage, and upgrading of laboratories and wet markets.

These activities typically generate wastewater high in organic matter, with some pathogenic or infectious, and solid wastes dominated by organic components that can be largely utilized. A small portion is composed of hazardous materials and waste, i.e., pathogenic, toxic, infectious, inflammable, and corrosive. All these have associated complex health and safety issues and biosafety risks too. Air emissions from vaccine production, laboratories, and hazardous waste incineration also contain infectious and toxic substances.

Addressing these issues requires assessing them first, through primarily an environmental impact assessment (EIA) process. This is being done in most countries and by international financial institutions (IFIs), such as ADB. The EIA can aid in decision-making and help optimize the project design to minimize its environmental consequences from the outset. Environmental impact that cannot be avoided or reduced through project design needs to be mitigated by treatment technologies and measures, such as those in an environmental management plan (EMP). All these are called environmental safeguards by IFIs and are well-illustrated in the preparation of both GMS One Health projects.

Assessing Risks and Mitigation Options

Wastewater treatment

Wastewater from vaccine production, livestock-holding facilities (e.g., breeding and quarantine centers), and slaughtering facilities are all high in organics in terms of high biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), and varying pathogenic substances. This was confirmed by baseline investigation and sample tests conducted during the EIA. The most suitable way to treat wastewater is through biochemical processes, also called secondary treatment. There are many kinds of technologies for decentralized biochemical treatment in a rural setting.

Technical experts proposed the decentralized wastewater treatment system (DEWATS) developed by German agency BORDA, which provided removal rates data. However, EIA analysis shows that DEWATS, followed by artificial wetland, will not be able treat wastewater of high organic concentration to meet even national discharge standards. Therefore, pre-treatment and/or post-treatment are needed. If these additional methods still fail, more effective yet affordable alternatives to DEWATS need to be considered. For subprojects with sufficient space or farmland nearby, outflow after treatment can be used to grow forage, which in turn improves the feed for animals, forming a true ecological circle.

For wastewater from vaccine production and laboratories, which is high in chemicals too, pre-treatment by neutralization, settlement, and floatation is needed to prevent acidic or alkalic chemicals from corroding pipes and equipment and disrupting the biochemical process. Wastewater from slaughtering is also high in grease that can disrupt the biochemical treatment process. Therefore, the EIA preparer suggested adding an oil trap as pre-treatment. Given that all wastewater above contains pathogens as well, stronger disinfection (e.g., by chlorination or ozone) is needed before final discharge.

In addition to the end-of-pipe treatment above, measures to reduce wastewater generated during operations are also included in the EMP. For animal holding and raising, dry scraping of the pen floor instead of conventional washing can reduce about one-third of wastewater. Preventing rainwater from entering wastewater ditches and treatment systems is also a good practice in many sectors.

Solid waste treatment

Subprojects with livestock-holding functions will generate solid wastes dominated by manure, bedding and feed residues, which are organic and relatively easy to utilize. The initial proposal by technical experts is to sun or wind dry them and then sell to farmers, which is the prevailing practice in these countries. However, the EIA estimated that waste volume can be several dozen tons per day for a quarantine center holding up to several thousands of pigs and hundreds of cattle based on the designed scale and applicable industrial norms and unit waste generation. This raised a series of questions: Are there sufficient farmlands within reasonable distance that could use this amount of manure wastes, especially considering the seasonality in fertilizer needs?

Such practice, when coupled with a bigger amount of manure, has exceeded the absorbing capacity of some areas and caused severe contamination of surface and groundwater. It has threatened drinking water supply and attracted pests and rodents with hygiene issues and strong odor, resulting in public complaints and even protest. In addition, is natural drying sufficient to kill pathogens for safe use in farmlands? Years ago in Germany, there was an incident of food poisoning because of agricultural produce contaminated by E. coli from a similar type of organic fertilizer.

These questions led the ADB environmental staff to propose the composting or digesting of organic wastes at bigger subprojects and sun/wind drying them at smaller facilities. The EIA compared the pros and cons and recommended such proposal. This method can turn wastes into better fertilizer or soil conditioner that is safer for users and agricultural products. It also dries them better, making them easier to transport and sell even to far-flung areas, thus alleviating the pressure on the local environment.

For pollution-generating projects, the EIA exercise inevitably needs to quantify future pollution levels (types, volume, concentration, among others) and evaluate if the treatment technology proposed can cut these down to meet applicable standards. However, meeting domestic standards is not easy for certain types of industries and subprojects, let alone international standards.

Hazardous waste treatment

Since most subprojects will generate hazardous wastes, though mostly in small amounts, the initial design by technical experts provided for an incinerator for each subproject as a standard method. Concerned about the incinerators’ fly ash and dioxin (which is also difficult and costly to monitor), poor operation and maintenance of small existing incinerators (i.e., only ~700 °C, without filter), as well as the budget shortage facing the subprojects, the EIA team and ADB environmental staff cautioned against such design and searched for other options.

Hazardous wastes from vaccine production, laboratories, and animal holding and breeding are mainly pathogenic and infectious. Can autoclave and other sterilization methods destroy most pathogens and turn them into non-hazardous general wastes? The answer from technical experts is positive but lacks details, such as what kind of sterilization should be used for which step in the production of specific vaccines. The production of different vaccines requires different intensities of sterilization according to literature. Sterilization can be achieved through different methods—such as autoclave, steam, dry heat, and chemicals—and each with different efficacy and cost. A feasibility study (FS) is tasked to compare various options (e.g., for sterilization) of a subproject based on technical requirements and financial considerations, and the EIA contributes to the FS by comparing options on environmental, health, and safety aspects.

Residual hazardous wastes need to be sent to the existing incinerator to be upgraded by the ADB projects or to a central one as suggested by the EIA, given that these subprojects are located 30 to 70 kilometers away from each other. This approach of reducing and converting hazardous wastes to general wastes as much as possible also exemplifies the long-proven fact that preventing pollution at source and reducing the process are much more efficient and cost-effective than end-of-pipe control.

The technical experts then considered upgrading an existing incinerator to treat all hazardous wastes of other subprojects in the vicinity. However, since the existing incinerator is located downtown, the EIA suggested two options. One is that the upgrade must improve incineration performance up to standard (i.e., 850°C for minimum retention time), higher stack (3–5 meters higher than the highest building in the vicinity) and fitted with filter, among others. The second option is to add a new incinerator at a subproject that is far away from residential areas and other sensitive receptors. It will then be up to the FS to evaluate the two options from a technical and financial perspective and reach a final decision.

Public Disclosure and Consultation

The EIA process has also helped the siting of subprojects. During baseline investigation of all proposed subprojects, the site of a new abattoir was found within a UNESCO biosphere. The technical experts and the host were immediately alerted to consult with the biosphere management authority in the country to check whether the abattoir and its designed scale can be allowed or not and what the required conditions are. As a result, different sites were proposed for the abattoir. 

As an indispensable part of the EIA process, public consultations began as early as possible. Initial consultation revealed that the COVID-19 pandemic has greatly raised public awareness of infectious diseases. Farmers’ main concerns include the possible spread of disease from livestock quarantine centers, chemical leaks from vaccine production and laboratories, and untreated wastewater and solid waste from livestock facilities. Partly due to these concerns and consequently, the desire for less pollution at the project facilities, the design of the quarantine center was modified to only inspect imported animals and not put them under quarantine for an incubation period normally required for disease control. However, such a change raises the concern about biosafety and health risks.

Limitation of the Environmental Impact Assessment

Not trained in epidemiology, veterinary science, or related health areas, environmental specialists were unable to argue with technical experts who considered that inspection without quarantine is sufficient to control diseases from animals imported from neighboring countries that have higher capacity, tighter control, and thus, lower risks. This shows the limitation of the EIA and the environmental specialists, the demands on whom are already overly multi-disciplinary and still increasing. In view of the EIA’s limitations and emerging needs, the health impact assessment (HIA) has been advocated by many in recent decades, including IFIs, such as ADB. So far, the efforts and guidance provided have largely focused on human health and not much on the zoonotic aspect.

The separation of human and animal health reflects the prevailing reality in most countries. Human health is managed by the Ministry of Health while animal health falls under the scope of the Ministry of Agriculture and its branches at the local level. Medical professionals seldom collaborate with veterinarians, let alone share waste treatment facilities, such as incinerators.

After more than 2 years of combating COVID-19, GMS countries have greatly increased their treatment capacity for health care wastes, including sterilization and incineration, with assistance from ADB, among others. If these new and enhanced facilities can also receive and treat animal-related hazardous wastes in surrounding areas, they can greatly improve the efficiency in controlling pollution and health and safety risks, setting a concrete example of One Health. The Ministry of Health in the project countries agreed to consider such idea despite the foreseeable difficulties.


The active promotion of good EIA practice—notably pollution quantification, more sample tests during baseline investigation, and more emphasis on comparing alternatives from an environmental perspective—has substantially increased the EIA’s role in a project’s design. As a result, this has enhanced the EIA’s relevance and contribution to One Health projects as more than mere compliance. As one of the three pillars of One Health, environmental health in reality, is mainly about pollution prevention and control to create and maintain a health-supportive environment.


A. Prüss-Üstün, 2016. Preventing Disease through Healthy Environments: A Global Assessment of the Burden of Disease from Environmental Risks. (link is external)World Health Organization.

Asian Development Bank. Cambodia Rapid Immunization Support Project under the Asia Pacific Vaccine Access Facility: Due Diligence of Cambodia’s Healthcare Waste Management System.(link is external) Manila.

Asian Development Bank (ADB). 2018. Health Impact Assessment, A Good Practice Sourcebook.(link is external) Manila.

ADB. 2018. Health Impact Assessment Framework for Special Economic Zones in the Greater Mekong Subregion.(link is external) Manila.

N. Mowat and M. Rweyemamu. 1997. Vaccine Manual: Veterinary Vaccine Production and Quality Control for Use in Developing Countries(link is external). Part III: Production Operations. Rome: UN Food and Agriculture Organization.

Occupational Safety and Health Administration (OSHA). 2011. Laboratory Safety Guidance.(link is external) United States.

World Health Organization (WHO). 2004. Laboratory Biosafety Manual.(link is external) Geneva.

World Organization for Animal Health (OiE). Terrestrial Animal Health Code.(link is external)

Ask the Experts

  • Xin Ren
    Senior Environmental Specialist, Southeast Asia Department, Asian Development Bank

    Once an ADB safeguard reviewer, Xin Ren now works on environmental issues in rural sector. Prior to ADB, she worked at World Bank on environment in diverse sectors. She also worked at UNEP and in the People’s Republic of China on waste management and clean production, and at UNFCCC on climate change.

This was originally posted on Development Asia.

Last Updated: 29 May 2022