Chemical contaminants in the environment

Did you know there are over 30,000 chemicals approved for use across Aotearoa New Zealand?

Who approves and regulates the use of these chemicals? How do we know what happens to these chemicals when they get into the environment? Are our regulations sufficient to stop contamination of waterways, land and oceans?

The Parliamentary Commissioner for the Environment set out to answer these questions in the report Knowing what’s out there: Regulating the environmental fate of chemicals.

The rules about how a chemical can be used shouldn’t be static – we need to be able to adapt as new information comes to light. Restrictions should be based on the latest science and informed by New Zealand-specific data on use and impact

Rt Hon Simon Upton, Parliamentary Commissioner for the Environment

To give a sense of how the regulatory framework works in practice, the report included four case studies of chemical substances. The case studies illustrate the way the regulatory system intervenes – or does not – to limit the impact of these chemicals on the environment. The four chemicals are:

• neonicotinoids – a class of insecticide
• tetracycline antibiotics
• the herbicide terbuthylazine
• the metal zinc

Who decides what chemicals can be used in New Zealand and how they can be used?

Four main regulators play a role in chemical management in New Zealand. The Environmental Protection Authority (EPA) is the key agency responsible for the management of any environmental risks associated with the use of hazardous substances. This means that, before a chemical can be used in New Zealand, the risks have to be assessed by the EPA. These include risks to human health and the environment. Not all chemicals get approved, and some can be banned later following a reassessment based on new evidence.

While the EPA approves the use of chemicals (as individual substances or under a group standard), other agencies have a role to play too. For example, the Ministry for Primary Industries (MPI) approves and registers agricultural compounds (such as pesticides and veterinary medicines), and Medsafe approves use of human medicines. From all agencies involved in the management of chemicals, the EPA is the only one looking at the potential impacts of chemicals on the environment.

If risks are identified during the assessment of a chemical, the EPA can restrict its use to limit the potential for harm. For example, once approved, some chemicals can only be used by people who have been trained how to use them. The EPA can also determine how a chemical is used by setting application rates (how much of a chemical can be used over specific time periods or areas) and buffer zones and prescribing label statements that give clear instructions about the risks.

What are chemical contaminants?

Chemicals are not inherently bad. Many – like medicines – help society. Not all chemicals have the same properties, and once in the environment, not all have the same level of persistence, mobility, bioavailability and toxicity. Decisions to approve, regulate or ban a chemical’s use involve judgements about what level of risk is acceptable in relation to the advantages it offers and conditions for how and where it will be used.

Problems arise when chemicals enter environments where they are not usually present or in quantities above naturally occurring levels. They become contaminants when they have the potential to cause problems for living things. Organisms can be mildly or severely affected by exposure to certain chemicals, and some can die. These contaminants can be natural (such as mineral compounds or human or animal waste) or human made (such as plastics and pharmaceuticals).

The report focuses on the impact of chemicals in receiving environments – where they are most likely to end up – such as freshwater ecosystems, coastal environments and soil.

How do chemicals get into our environment in the first place?

There are multiple ways in which chemicals enter the environment, including:

• direct application onto the land such as by spraying pesticides on lawns or crops
• leaching out of landfills (when they’re not properly lined), storage facilities, manufactured items or from naturally occurring sources
• they can be carried in run-off from roofs and roads into stormwater drains reaching waterways after a rain event
• discharge of treated sewage from wastewater treatment plants that may still contain traces of some chemicals.

What happens to chemicals in the environment?

Once a chemical is in the environment, its physical and chemical properties will influence where it ends up and whether it will have any toxic effects on organisms and ecosystems exposed to it. Based on these properties and observational work, scientists have developed tools to measure:

• persistence – how long a chemical remains in the environment
• mobility – how far a chemical can move from its source to, within or through a receiving environment
• bioavailability – how much is likely to be available to organisms to take up
• toxicity – how a chemical can harm an organism.

The persistence of a chemical in the environment will depend on how easily it degrades. Key environmental factors affecting the rate of a chemical’s degradation include exposure to:

• photolysis (light)
• hydrolysis (water)
• biodegradation (microbial activity).

Mobility is affected by interactions with other chemicals or non-biological factors such as pH (acidity), temperature, dissolved organic matter or salinity. A chemical can be transported through different pathways, including soil, water or air, meaning living things can be exposed to chemicals through different routes.

In the environment, only a portion of the total amount of a chemical is potentially available to be absorbed or taken up by an organism. This is referred to as bioavailability.

Do we know what chemicals end up in the environment and where?

Monitoring of chemicals and the many related compounds in New Zealand is very patchy. Fewer than 200 chemicals – of the roughly 30,000 approved for use – are routinely monitored by national (state of the environment reporting) or regional monitoring programmes.

Report findings and recommendations to fix the identified problems

The report Knowing what’s out there: Regulating the environmental fate of chemicals makes several recommendations to help the government keep a better track of what chemicals are reaching the environment.

The Commissioner recommended that the quantities of chemicals imported, manufactured, sold and used be fed back to the regulatory system so regulators know where they have been used.

We cannot monitor every single chemical in New Zealand, but we should monitor the riskiest chemicals. These should be prioritised based on their scale of use, potential harm and environmental presence. The design of any framework should involve Māori.

Once identified, actual levels of the riskiest chemicals for environmental contamination should be monitored and compared against appropriate guidelines and limits. Ideally, the results would be reported back so rules for the chemical can be adjusted if needed. This would help make sure we have New Zealand-specific data for the chemicals we’re most worried about.

The best way to prioritise which chemicals to monitor is to consider those that are present in the environment at a large scale and are known to be harmful to the environment and human beings.