Ocean pollution

The oceans are under increasing stress from multiple urban and rural sources of pollution, notably solid and liquid wastes from cities, fertiliser and manure run-off from farming, air emissions from shipping, and incorrect disposal of plastic from land-based and sea-based sources.

The OECD is supporting governments to adequately address these challenges. The cumulative effects of ocean pollution can be devastating for human well-being and ecosystem health. Ultimately, they can undermine sustainable economic growth. The OECD provides policy insights on managing and preventing water pollution and marine plastic waste, and reducing the environmental impacts of shipping.


Marine plastic waste

Plastic waste is present in all the world’s ocean basins, including around remote islands, the poles and in the deep seas. Accumulating in the natural environment, plastics will only decompose over hundreds or even thousands of years.

A majority of marine plastic waste  originates from land-based sources and is transported to the ocean through rivers, with the remaining share of debris coming from fishing activities, natural disasters and other sources. Marine debris encompasses large objects, microplastics and nanoplastics, which entangles or is ingested by species who live in them. Microplastics may travel up the food chain and pose potential risks to human health once ingested. Marine litter also leads to a range of socioeconomic impacts to tourism, fishing and aquaculture, and shipping.

Plastic waste prevention

Plastics waste can be prevented by leveraging incentives along the value chain, as well as by addressing negative externalities associated with plastics production upstream, and plastics waste generation and littering downstream.

Policy interventions to foster plastic waste prevention include the introduction of price signals (e.g. through taxes on disposable plastic goods or deposit-refund schemes for reusable packaging), product bans for particularly harmful products which are prone to leakage but unlikely to be collected and recycled (e.g. microbeads), product durability standards and consumer education campaigns.

Waste management

Improvement of waste management systems can help ensure adequate end-of-life treatment of plastic waste. It is estimated that between 14 to 18% of waste plastics generated globally are collected for recycling and 24% is incinerated. The remainder is disposed of in landfills, via open burning or uncontrolled dumping, or released to the wider environment.

Stopping the leakage of plastic waste into the ocean requires strengthening waste collection, recycling and disposal systems. In developing countries, official development assistance could be leveraged to support the development and operation of effective collection systems and waste-treatment infrastructure.

Key publication

Improving Markets for Recycled Plastics: Trends, Prospects and Policy Responses Plastics have become one of the most prolific materials on the planet: in 2015 we produced about 380 million tonnes of plastics globally, up from 2 million tonnes in the 1950s. Yet today only 15% of this plastic waste is collected and recycled into secondary plastics globally each year. This report looks at why this is the case and what we can do about it, as the pervasiveness of plastics has become an urgent public health and planetary problem. 

Managing and preventing water pollution

Improving water quality from source-to-sea requires managing both point and diffuse sources of pollution. One of the main policy challenges facing OECD countries is the effective management of diffuse sources of nutrient pollution, which are caused by activities that have no specific point of discharge, and are often linked to agricultural and urban pollution via overland flow to surface waters.

Unless attention is turned to these diffuse sources, further deterioration of water quality and the ocean can be expected as human populations grow, industrial and agricultural production intensifies, and climate change causes significant alteration to the hydrological cycle.

Globally, one of the most prevalent water quality challenges is eutrophication; a form of water pollution caused by excess use of nutrients (nitrogen and phosphorous). Eutrophication can trigger toxic algal blooms and cause “dead zones” (oxygen depletion) in the ocean and coastal waters leading to significant loss of marine biodiversity. Excessive nitrogen in the environment also contributes to climate change, depletion of the ozone layer, air pollution, nitrate toxicity in groundwater and drinking water, loss of biodiversity and deterioration of soil quality.

Key publications


Human Acceleration of the Nitrogen Cycle: Managing Risks and Uncertainty examines the risks associated with the release of excessive nitrogen into the environment (climate change, depletion of the ozone layer, air pollution, water pollution, loss of biodiversity, deterioration of soil quality). The report also examines the uncertainty associated with the ability of nitrogen to move from one ecosystem to another and cause "cascading effects". This report provides guidance on the use of nitrogen policy instruments and how to ensure coherence with objectives such as food security, energy security and environmental objectives.


Diffuse Pollution, Degraded Waters: Emerging Policy Solutions outlines the water quality challenges facing OECD countries today, presents a range of policy instruments and innovative case studies of diffuse pollution control, and concludes with an integrated policy framework to tackle diffuse water pollution. An optimal approach will likely entail a mix of policy interventions reflecting the basic OECD principles of water quality management – pollution prevention, treatment at source, the polluter pays and beneficiary pays principles, equity, and policy coherence.

Environmental impacts from shipping

Global shipping is responsible for approximately 30% of total global nitrogen oxide (NOx) emissions. These emissions have been  linked to thousands of premature deaths in coastal areas. Ships account for approximately 2.5% of total global greenhouse gas (GHG) emissions. Other environmental impacts from shipping include biodiversity impacts related to ballast water and the effect of noise pollution on ocean wildlife. Global policy efforts have recently focused on sulphur and GHG emissions from ships and ballast water management, but efforts could be intensified with respect to NOx and particulate matter (PM) emissions.

 The International Transport Forum (ITF) at the OECD has conducted various studies that aim to provide policymakers with tools to reduce air emissions from shipping.

Key publication

Decarbonising Maritime Transport: Pathways to zero-carbon shipping by 2035 examines what would be needed to achieve zero CO2 emissions from international maritime transport by 2035. It assesses measures that can reduce shipping emissions effectively and describes possible decarbonisation pathways that use different combinations of these measures. In addition, it reviews under which conditions these measures could be implemented and presents concrete policy recommendations.