A systematic review published in the Journal for the American Heart Association looks at ocean microplastic pollution and the risk of cardiometabolic disease in US coastline counties.
Prof Oliver Jones, Professor of Chemistry, RMIT University, said:
“I fear this paper will lead to more “plastics cause scary disease X” headlines, but, to my mind, the evidence in this paper is quite weak.
“Firstly, the authors don’t claim that microplastics cause disease, but rather that they found an association between microplastic exposure and type 2 diabetes (T2D), coronary artery disease (CAD), and stroke. An association between two things does not necessarily mean that one caused the other; it is simply an observation. There is also a large amount of overlap in the datasets, even between the very low and very high exposure scenarios, and the authors clearly state in the paper that their “results do not imply causation”.
“Perhaps more importantly, the authors didn’t measure either microplastic exposure or the health factors they studied directly; both were estimates. Microplastic concentrations were estimated from ocean measurements, some of which were taken up to 230 miles offshore and thus may not accurately represent what coastal communities are exposed to. The rates of disease occurrence were estimated from county-level survey data, which does not provide data on individuals. Potential cofounders were limited to those listed in the survey data, meaning some potentially confounding factors could not be controlled for.
“The authors all appear to be medics, rather than chemists or environmental scientists. The paper makes a lot of incorrect generalisations about microplastics, for example, referring to “microplastic compounds like phthalates”. Phthalates are not microplastics, and not all phthalates are the same. They claim that bisphenol A and phthalates promote adverse health outcomes through their endocrine-disrupting properties, which is incorrect. The paper also refers to toxicity studies on polystyrene particles, neglecting the fact that polystyrene is far from the most common type of plastic in the environment.
“So, while the work raises interesting research questions, I do not think the evidence of harm is strong, and people living near the coast don’t need to panic”
Dr Ria Devereux, Environmental Research Fellow, the Sustainable Research Institute, the University of East London, said:
Does the press release accurately reflect the science?
“It is important to note that this research focuses solely on the United States, particularly its coastal counties, and specifically examines marine microplastics. It does not consider other types of microplastics, such as those found in marine sediment, beach sediment, atmospheric microplastics, or microplastics in soil. The title, “Living near an ocean polluted by microplastics may increase cardiometabolic disease risk,” could give the incorrect impression that these findings apply globally, which is not justified by this data.
“Both sizes of plastic particles come from the chemical breakdown (decomposition) of larger plastic waste, including food packaging (like single-use water bottles), synthetic fabrics and personal care products.” This statement is also slightly incorrect. Microplastics can also be found in the form primary microplastics (nurdles) which are made to be a particular size and are not the result of degradation. Plastics are also subjected to mechanical, biological degradation as well as chemical.
Is this good quality research? Are the conclusions backed up by solid data?
“It is very interesting research which does need further research to investigate some of the limitations of the study conducted. One major limitation that is not addressed is that microplastics contain chemicals which have been found to be harmful to human health. There is no mention in this study regarding data on water quality. For example, is there a higher abundance of chemicals found within plastics in the water surrounding these coastal communities which may be a contributing factor.
How does this work fit with the existing evidence?
“The production of plastic and its associated pollution are increasingly recognized for their potential implications on human health. Research conducted on wildlife has demonstrated severe consequences, including choking hazards and hormonal disruptions.
“Recent studies have identified plastics in various human tissues, including the placenta [1],breastmilk [2] and stool [3].
“In addition to the presence of microplastics in the human body, chemicals commonly used in plastic production have been found to pose health risks. Research indicates that exposure to these chemicals can lead to various health issues, including skin irritation, respiratory diseases, hormonal disruptions, and certain cancers [4].
Have the authors accounted for confounders? Are there important limitations to be aware of?
“The dataset from NOAA presents several limitations. It does not account for when the samples were collected—such as during storms—or the duration of the sampling periods. Additionally, there may be a lack of studies in many coastal counties. For instance, most samples from the Gulf of Mexico are concentrated around Tampa and the southern region of Florida, with only two data points near New Orleans. While the authors briefly mention this issue in relation to the Atlantic and Pacific coasts, they do not address it for the Gulf of Mexico. They note that “study design, spatial coverage, and oceanic transport dynamics” may contribute to differences observed in previous studies.
“The authors also acknowledge that the absence of data on the types of microplastics—such as fragments and fibers—constitutes a limitation. However, this statement should also include the lack of information regarding polymer types and plastic sizes.
“Additionally, it would be relevant to consider how many people in these coastal areas consume seafood and whether it is locally sourced or imported.
“As for the timeframe investigated, How long must someone live near the coast for it potentially to impact their health?
“Regarding groundwater, the authors mention that only “35% of drinking water in the United States is supplied by groundwater.” Is the proportion of coastal residents who drink groundwater higher than that of individuals living in other parts of America?
“Perhaps the most critical issue that the authors have not fully addressed is that almost all plastic production plants in the United States, which are involved in petrochemical and petroleum manufacturing, are located either in coastal counties along the Gulf of Mexico or on the Atlantic Ocean side (according to the Plastics Inventory Map [5]). This study indicates that cases of heart disease and similar health issues are higher in these areas. Many chemicals used in plastic production, such as BPA and phthalates, have been previously linked to these health problems [6]
What are the implications in the real world? Is there any over-speculation?
“This study highlights the need for further investigation into the health impacts of plastics on human well-being throughout their entire lifecycle. While this research primarily focuses on marine microplastics, it is essential to recognize that microplastics are also present in soil, air, and water. Additionally, it is important to understand that the risks associated with plastic do not stop at ingestion or inhalation, the entire lifecycle of plastic poses threats to public health. This includes hazards linked to petroleum extraction, the use of chemicals in production, and the leaching of these substances into our environment during manufacturing and disposal.
“It is important to note that this study cannot establish a cause-and-effect relationship between ocean microplastic levels (which were assessed only in water, not in sediment or fish) and the development of certain diseases due to its limitations in data and design. Further research is needed to determine whether microplastics and associated chemicals are present in higher concentrations near coastlines in soil, water, and air, as well as within the human body, to fully evaluate the potential health implications of living closer to the coast. Additionally, this study should be expanded to explore whether this trend is observed worldwide.
“Unfortunately, many individuals around the globe view plastic pollution solely as an environmental issue, overlooking its potential implications for human health. Studies like this one play a crucial role in raising awareness of these risks.
Extra commentary from Dr Ria Devereux on wider context
“The adverse effects of chemicals used in plastic production are particularly pronounced in the Gulf of Mexico, an area often referred to as “Cancer Alley.” This region experiences a higher-than-average incidence of cancer, diabetes, and respiratory diseases, which are concentrated in particular areas. The reason behind this is the concentration of petrochemical, petroleum and production plants involved in plastic production and an increase in the presence of chemicals used within the plastic production such as BPA and Phthalates [7,8].
“Although the Plastics Treaty acknowledges that human health is a critical factor in regulating plastic production and the associated chemicals, reports indicate that “chemicals of concern in plastic products” are at threat of being excluded from the current treaty text [9,10,11].
“In regards to America, we may find in the future that this types of disparity in human health and microplastics become worse due to Trumps “America first” narrative on top of increasing tariffs which will cause an increase in the plastics industry to align with the needs of the consumer and manufacturers. On top of this Trump has bought plastic straws back to America [12] and has started to dismantle key government institutions such as NOAA ( The National Oceanic and Atmospheric Administration)[13] and the Environmental Protection Agency [14] which will push back Americas efforts to reduce plastic waste.”
1 – https://www.sciencedirect.com/science/article/pii/S0160412020322297
2 – https://www.mdpi.com/2073-4360/14/13/2700
3 – https://www.acpjournals.org/doi/abs/10.7326/M19-0618
4 – https://www.sciencedirect.com/science/article/pii/S0013935124004390
5 – https://eipmaps.maps.arcgis.com/apps/instant/basic/index.html?appid=ebb37bd4fefb481db69c500b3f1f69e7
6 – https://pmc.ncbi.nlm.nih.gov/articles/PMC8335843/
7 – https://www.theguardian.com/us-news/2021/may/17/st-james-parish-formosa-complex-biden-cancer-alley
8 – https://digitalcommons.law.villanova.edu/cgi/viewcontent.cgi?article=1440&context=elj
9 – https://www.science.org/doi/10.1126/science.adf5410
10 – https://news.un.org/en/story/2024/11/1157326
13 – https://www.theguardian.com/us-news/2025/jun/11/climate-website-shut-down-noaa
‘Marine Microplastic Levels and the Prevalence of Cardiometabolic Diseases in US Coastline Counties’ by Makwana et al. will be published in Journal for the American Heart Association at 10:00UK time on Wednesday 18th June.
DOI: 10.1161/JAHA.124.039891
Declared interests
Dr Ria Devereux None
Prof Oliver Jones “I am a Professor of Chemistry at RMIT University in Melbourne, Australia. I conduct research into environmental pollution and its effects on biological systems. I don’t have any conflicts of interest to declare.”