According to research reviewed by Gram, people in New Zealand who eat dairy products may take in roughly 9.2 to 40 nanograms of bromoform per kilogram of body weight per day, and cheese and liquid milk were the main sources. The study’s authors concluded that cancer and non-cancer risks from these levels appear negligible.
Researchers wanted to know what would happen if farmers used bromoform, a chemical found in certain red seaweeds, to reduce methane from dairy cows. Using data on how much of the chemical shows up in milk products and how New Zealanders eat, the team estimated how much people might consume. Adults and children would likely take in small amounts, with the highest intake usually found in younger people. Cheese and liquid milk were the biggest sources. According to research reviewed by Gram, the estimated cancer and non-cancer risks appear negligible. The findings come from a modeling study, not a direct test in people, so they offer a useful early estimate rather than a final verdict on safety.
Key Statistics
A 2026 modeling study published in Food Additives & Contaminants Part A estimated that average dietary bromoform exposure from dairy products in New Zealand ranged from 9.2 to 40 nanograms per kilogram of body weight per day across age groups.
The same 2026 study estimated that high-end dietary bromoform exposure, at the 95th percentile, ranged from 22 to 100 nanograms per kilogram of body weight per day, with cheese and liquid milk as the largest contributors.
The Quick Take
- What they studied: If bromoform were used to cut methane from dairy cows, how much of it could people eat through milk and cheese, and would that amount pose a health risk?
- Who participated: No people took part directly. The researchers used existing data on bromoform levels in processed dairy products and national diet patterns in New Zealand and other countries. The sample size was not specified.
- Key finding: Average estimated intake ranged from 9.2 to 40 nanograms per kilogram of body weight per day across age groups, and high-end intake (the 95th percentile) ranged from 22 to 100 nanograms. The authors judged the risks from these amounts to be negligible.
- What it means for you: Based on this modeling, the amount of bromoform that could reach people through dairy appears very small. No change to your diet is needed based on this study alone, but future real-world testing would give a clearer picture.
The Research Details
Bromoform is a chemical that red seaweeds such as Asparagopsis taxiformis and A. armata naturally produce. It can reduce methane, a gas released by cows that contributes to climate change. Some companies are also developing bromoform made outside of seaweed for the same purpose. Bromoform belongs to a family of chemicals that includes chloroform, which can form in tap water during disinfection.
The researchers did not test people. Instead, they combined two kinds of information. The first was recent measurements of how much bromoform remains in processed milk products such as cheese and liquid milk. The second was data on how much of these foods people in New Zealand and other countries typically eat, broken down by age. By combining these numbers, they estimated how much bromoform a person might take in each day, based on body weight.
They calculated both average intake and high intake, the latter representing the upper 5 percent of consumers. This approach lets researchers look at a realistic typical case and a worst-case-leaning scenario. They then compared these estimates with health reference values to judge whether the risks were a concern.
A modeling approach like this lets scientists estimate possible exposure before a new practice is widely used. Because the substance is not yet in common use on farms at scale, it is not possible to measure real-world intake in the population. Using existing residue data and diet records gives an early, evidence-based estimate that helps regulators decide where more testing is needed.
The study is published in a peer-reviewed food safety and chemistry journal, which means other experts reviewed it before publication. It uses real measured residue data and national diet surveys, which strengthens its estimates. However, the results depend on assumptions about how much bromoform ends up in dairy and how people eat, so they are estimates rather than direct measurements. The sample size is not specified, since the work is based on existing datasets rather than a new group of participants.
What the Results Show
The estimated average daily intake of bromoform from dairy products ranged from 9.2 to 40 nanograms per kilogram of body weight across age groups. A nanogram is one billionth of a gram, so these amounts are extremely small. The researchers expressed intake relative to body weight so that people of different sizes could be compared fairly.
Intake generally decreased as people got older when measured per kilogram of body weight. Young children tend to eat relatively more food for their size, so their estimated exposure was higher. This pattern matched what the researchers expected from typical diet and body size differences.
For high-end consumers, the estimates reached 22 to 100 nanograms per kilogram of body weight per day. Cheese and liquid milk were the largest contributors to these totals, since people eat them regularly and in fairly large amounts. Other dairy products contributed less.
Based on these intake levels, the authors concluded that both non-cancer and cancer risk estimates for the New Zealand population were negligible. They described the potential presence of bromoform in dairy products as posing very low risk under the scenario they modeled.
The study highlights that dairy products are the main route through which bromoform could reach people if it were used in cattle feed. This points to where future monitoring efforts should focus. The findings also show that exposure estimates can be compared across age groups, which helps public health planners consider vulnerable populations such as young children.
Bromoform and related chemicals such as chloroform are already known as disinfection by-products in drinking water. Regulators have long assessed their health effects at low levels, which gives this study a reference framework. This research adds information specific to dairy products in the context of a new agricultural use, building on earlier work on seaweed-based feed and residue testing.
The study does not measure bromoform in people’s bodies, so it cannot confirm actual intake. Its estimates depend on the residue data and diet information available, which may not reflect every dairy product, farm practice, or region. If feed use increases substantially or differs from the scenarios modeled, actual levels could change. The sample size is not specified, and the analysis focuses on New Zealand, so results may not apply directly to other countries with different diets or farming methods. Long-term effects at these low levels are also a topic that requires continued study.
The Bottom Line
Based on this modeling study, there is no evidence that dairy products containing bromoform residues would pose a meaningful health risk at the levels estimated. Confidence in this conclusion is moderate, since it rests on modeled estimates rather than direct measurements in people. Continued residue testing and real-world monitoring would strengthen the evidence before wider use.
Dairy farmers, food safety regulators, and researchers working on methane reduction should pay close attention, since these results inform whether bromoform feed additives are safe to use. Parents of young children may find the age-related patterns informative. Most everyday consumers do not need to change their habits based on this study alone. People with specific health conditions or concerns about chemical exposure should talk with a healthcare provider.
Results from a modeling study like this do not produce immediate changes in diet or health. Any real effect on consumers would depend on whether bromoform feed additives are adopted on farms and how regulators respond. Monitoring and follow-up research could take several years to produce clearer, real-world data.
Frequently Asked Questions
Is bromoform from cow methane feed safe in milk and cheese?
A 2026 modeling study estimated bromoform intake from dairy at 9.2 to 40 nanograms per kilogram of body weight per day on average. The authors judged cancer and non-cancer risks to be negligible, though the findings rely on modeled estimates rather than direct testing in people.
What is bromoform and where does it come from?
Bromoform is a chemical related to chloroform that certain red seaweeds naturally produce. It can reduce methane released by cows, and some companies are developing it in non-seaweed forms. It is also in the same chemical family as some water disinfection by-products.
Which dairy foods contain the most bromoform?
Cheese and liquid milk were the largest sources of dietary bromoform exposure in a 2026 New Zealand modeling study. Their high consumption levels drive most of the estimated intake, while other dairy products contributed less to the total.
Do young children get more bromoform from dairy than adults?
When measured per kilogram of body weight, estimated bromoform exposure from dairy generally decreased as people got older. Children eat relatively more food for their body size, so their estimated intake per kilogram was higher than adults'.
Want to Apply This Research?
- Log the number of servings of cheese and milk you eat each day in your app, using a standard serving size such as one cup of milk or one 30-gram slice of cheese. Reviewing these totals weekly gives you a clear picture of your dairy intake over time.
- There is no need to cut dairy based on this research. If you want to vary your intake, you can rotate between cheese, milk, yogurt, and non-dairy options so that no single food dominates your diet. Keep portions consistent with national dietary guidelines.
- Check the app’s monthly summary of dairy servings and watch for major changes in your habits. Set a reminder to review updates from food safety agencies as new residue testing and regulatory decisions about bromoform feed additives are published.
This article summarizes a modeling study that estimates possible exposure to bromoform from dairy products. It did not test people directly and is not medical advice. Anyone with health concerns about chemical exposure or dietary choices should talk with a qualified healthcare provider or registered dietitian.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.