Log In Sign Up

Why the EPA is reversing course on perchlorate standards

The US Environmental Protection Agency has moved to reverse course on perchlorate, an oxidiser used in fireworks, ammunition, aerospace components and some industrial processes. Its January 2024 rule set the first federal drinking-water limit at 9 micrograms per litre (µg/L), equivalent to 9 parts per billion, for public water systems.

For Australians, this is not a change to tap-water law: a US EPA decision does not govern Sydney, Melbourne or any other local supply. It matters as a case study in how regulators balance thyroid risks, occurrence data and treatment costs for a contaminant that is widespread but usually found at low concentrations.

From national limit to proposed withdrawal

The standard followed more than a decade of petitions, scientific reviews and public comment. It required new monitoring and laboratory methods, with compliance initially due in 2027. In October 2024, the EPA delayed the deadline to 2029 while reconsidering the rule.

The agency proposed rescission in May 2025, arguing it needed a better framework and more current information on occurrence and treatment. As a rulemaking proposal, not an immediate repeal, the existing requirements remain relevant until the process is completed.

The health science behind the dispute

Perchlorate can interfere with the thyroid’s uptake of iodine. The concern is greatest during pregnancy and infancy, when disrupted thyroid hormone supply can affect development. The EPA’s original limit sought to protect sensitive groups, while its newer position argues that concentrations below roughly 10 µg/L do not present a significant health risk.

That does not mean every detectable amount is harmless. Researchers warn the reversal could create false confidence for infants and people with thyroid conditions. The dispute is about where evidence supports a line between acceptable exposure and preventable risk.

Why treatment costs drive the debate

Removing perchlorate can require ion exchange, reverse osmosis or specialised activated carbon, depending on water chemistry. Plants must dispose of spent media or brine, and small rural systems can face costs that are large relative to their revenue. EPA modelling in 2024 projected hundreds of millions of dollars in annualised compliance costs, while estimated health gains depended on contested exposure assumptions.

Supporters of the reversal call that imbalance; critics call it a rollback that shifts costs to households, states or less affluent communities. The figures do not settle who should pay to reduce a small risk, especially where EPA estimates indicated millions could be affected.

How data and lobbying changed the debate

Occurrence estimates remain the weak point. Perchlorate is highly mobile in groundwater, can enter surface water through rain and runoff, and may occur naturally in some deposits. Better local data can show where a national average is misleading, but it can also support targeted treatment rather than plant-wide upgrades.

Chemical and water-industry groups have pressed the EPA to account for feasible treatment and reliable data. Their lobbying is only part of the story. The reversal also fits a wider US push to revisit recently tightened drinking-water rules, giving the debate a broader political context.

What withdrawal would and would not do

If finalised, rescission would remove the 9 µg/L national drinking-water requirement and its federal monitoring programme. It would not ban perchlorate, authorise industrial discharges or make contaminated groundwater lawful. Clean Water Act permitting duties and state rules would continue, and the EPA would retain authority to respond if new evidence showed a material risk.

California already imposes a stricter 5 µg/L limit, so withdrawal would not produce uniform protection. Utilities could still monitor voluntarily, negotiate treatment with polluters or use source controls. The result may be a patchwork rather than a clean national reset.

What the decision means for Australia

Australia follows the Australian Drinking Water Guidelines, developed by the National Health and Medical Research Council and applied through state and territory regulators and utilities. A US EPA vote cannot alter Australian limits, and there is no single federal perchlorate maximum here. Sydney Water and Melbourne Water publish water-quality information for their systems, offering a route for local scrutiny.

Perchlorate can reach the Australian market through fireworks sold for New Year celebrations and sporting events, ammunition, aerospace and industrial supply chains. Not every pyrotechnic product contains it, and formulations vary. Australian Border Force, dangerous-goods licensing and the AS 1906 fireworks standards are more immediate controls than the US drinking-water rule.

Local businesses and consumers should examine products and sources rather than react to a distant policy change. Imported fireworks can enter through several ports and distribution channels, while military or industrial sites require careful groundwater management.

Practical checks for Australian households and suppliers

Households should treat the US proposal as context, not evidence that Australian tap water is unsafe. A useful local check is the latest report from the relevant water utility or state regulator, especially for supplies near industrial or defence activity.

For households

Utilities, regulators and importers can focus on source-specific controls rather than copying a US-wide number.

For suppliers and regulators

Follow CAPosts.com’s science and environment coverage for verified updates, bookmark this report and share the evidence-based summary with colleagues, parents and local representatives.