Plastics are all around us. They are used in everything from tents to trains and are often part of the packaging that surrounds our food and drink products.

Produced from a range of chemicals and in a variety of ways, plastics have become intertwined with modern life, often replacing wood, metal, and other more expensive and less hardy materials.

One group of chemicals often found in plastics are phthalates. These increase the flexibility, transparency, durability, and longevity of plastics. Phthalates are commonly used in food packaging, medications, toys, and even medical devices.

Over recent years, there have been discussions around the safety of phthalates, and, as a result, they are gradually being replaced in many products in Canada, Europe, and the United States. However, there is no definitive evidence that they cause serious illness, and millions of tons of phthalates are still used globally each year.

Phthalates and disease in the spotlight

A study published this week in the journal Environmental Research takes a fresh look at the links between phthalates and long-term health. The researchers involved are based at the University of Adelaide and the South Australian Health and Medical Research Institute. The team was headed up by associate professor Zumin Shi, from the University of Adelaide's Medical School.

In this study, which is the first to explore total phthalate exposure among Australian males, data were taken from 1,500 men. Phthalates were detected in 99.6 percent of the men aged 35 or older.

This matches up with previous work showing that increasing age and Western diets are associated with higher concentrations of phthalates. Earlier studies have also shown that phthalate levels are higher in men who consume more packaged and processed foods, more carbonated soft drinks, and less fresh fruits and vegetables.

Levels of the chemicals in each individual were then matched up with chronic diseases.

"We found that the prevalence of cardiovascular disease, type 2 diabetes, and high blood pressure increased among those men with higher total phthalate levels." Prof. Zumin Shi

Even once the data were adjusted for lifestyle and socioeconomic factors, the results remained relatively unchanged.

Similarly, although 82 percent of the men involved in the study were overweight or obese - which are conditions known to increase the risk of several chronic diseases - once the researchers adjusted their analysis to account for this, the results were still significant.

Do phthalates cause disease?

Earlier research into phthalate levels has produced similar results, finding a relationship with cardiovascular disease, type 2 diabetes, and hypertension. However, previous studies have often used women, children, or elderly populations. As aforementioned, this study is the first to look at the relationship between phthalates and chronic disease in middle-age and older men.

The current study cannot prove cause or effect - in other words, it is not clear whether the higher levels of phthalates cause the chronic conditions, or whether the higher levels are a result of disease-related processes. Although, as Prof. Shi explains, some believe that there could be a causal link.

"While we still don't understand the exact reasons why phthalates are independently linked to disease, we do know the chemicals impact on the human endocrine system, which controls hormone release that regulate[s] the body's growth, metabolism, and sexual development and function."

Alongside the connection between elevated phthalate levels and chronic disease, the team also found that higher levels are associated with an increase in inflammatory biomarkers. This backs up other work demonstrating the pro-inflammatory effects of phthalates.

Chronic diseases, such as cardiovascular disease and type 2 diabetes, are often referred to as lifestyle diseases. This is because lifestyle factors, such as inactivity, diet, and smoking, play a significant role in their development.

However, over recent years, there has been interest in examining other potential environmental factors that might be at work, and phthalate ingestion is one such factor.

Although the study leaves us with more questions than answers, Prof. Shi gives some sound advice, saying, "While further research is required, reducing environmental phthalates exposure where possible, along with the adoption of healthier lifestyles, may help to reduce the risk of chronic disease."

These researchers join the ranks of others who have found a correlation between phthalates and disease. Next, an important and much more difficult question needs answering: is it a causal relationship?