Stainless Steel vs. Plastic: Pros & Cons

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I was surprised to read a comment by one of The Filtery’s visitors who was dismayed by my apparent preference of stainless steel over plastic. In fact, they thought I should actually prefer certain types of plastic over stainless steel—at least for some things.

I appreciate all readers’ comments and take them seriously. So, in the interest of truth, I decided to dive deeper into the topic of the pros and cons of stainless steel vs. plastic.

In this article, you’ll find the results of my investigation clearly laid out. I’ve done my due diligence and analyzed life cycle assessments (LCAs) conducted by independent researchers who aren’t affiliated with or receive funding from the industries whose materials they’re scrutinizing. (This is needed to protect against bias.)

Through my research, I learned a few things about stainless steel vs. plastic, and I hope you will, too. Most of all, I hope you’ll find this information helping guiding your purchasing decisions.

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Is chromium leached from stainless steel toxic?

Stainless steel is a mainly non-reactive mixture of metals—mostly iron with small amounts of chromium and nickel. 

First of all, it’s very important to note here that the form of chromium in stainless steel is chromium-3 (aka chromium picolinate) not chromium-6 (aka hexavalent chromium), a known drinking water contaminant. (Chromium-6 is “the Erin Brockovich chemical”!)

Chromium-6 is toxic, but chromium-3 is an essential trace mineral that is found in many foods and is essential for human health in small amounts.

There is little recent evidence of chromium or nickel metals leaching into food or beverages, but a 2013 study showed it is possible when acidic foods (for example, tomato sauce) are heated for long periods in certain stainless steel grades. This is especially true for brand new stainless steel. Repeated uses (6+) decrease the amount leached to acceptable levels. 

(So, in theory, if you were really worried about this, you could heat and re-heat a jar of tomato sauce in your brand new stainless steel pot 6 times before actually using it for the first time.)

What is an acceptable chromium level? The Mayo Clinic advises people who take chromium-3 supplements (again, humans require a little chromium each day for metabolic functioning) that up to 200 micrograms/day (less than the weight of a single grain of sand) is okay. That’s about what new stainless steel leached in tomato sauce after being heated for a long time according to the previously cited study. 

So: chromium leached from stainless steel is not toxic.

Is nickel leached from stainless steel toxic?

The Dartmouth Superfund Research Program states nickel is likely an essential nutrient for humans in minute amounts. It’s ubiquitous in food, water, and air. 

According to the above study, humans ingest roughly 170 micrograms per day. This is approximately what brand new stainless steel may leach into certain foods. So, nickel leached from stainless steel is not toxic.

Unless you are one of the few people (5-10% of the population) with a nickel allergy, who should avoid stainless steel just in case nickel leaches out, stainless steel presents minimal negative health impacts. Nickel allergies are mostly a problem for those working in factories where nickel is processed.

Plastic leaches all kinds of toxic chemicals

Plastic, on the other hand, is an entirely different story. Since there are many different types of plastics, I can’t make broad generalizations. However, a 2021 study revealed some pretty terrible information about plastic leachates under realistic conditions (for example, from a water bottle). 

The investigators looked at 24 common plastic objects, each made of one out of eight plastic types. After 10 days at 104°F, they analyzed the chemicals that migrated in vitro. All migrates induced baseline toxicity, 22 elicited an oxidative stress response, and 14 showed endocrine-disrupting activity.

What was disturbing is that of the thousands of migrating chemicals, most were unknown. Therefore, I can be sure they have never been tested for safety.

Specifically, the researchers concluded that between 1 and 88% of the plastic chemicals in a single product were migrating, but could identify only roughly 8% of them!

In other words: despite everything we currently know about how toxic plastic chemicals can be, we have still only scratched the surface.

Polyvinyl chloride (PVC), polyurethane (PU), and low-density polyethylene (LDPE) induced the most toxicity, but they couldn’t make generalizations for other materials because the compounds were unknown. 

They concluded: “Our results demonstrate that plastic products readily leach many more chemicals than previously known, some of which are toxic in vitro. This highlights that humans are exposed to many more plastic chemicals than currently considered in public health science and policies.”

Just like with stainless steel, high temperatures could make them leach more easily. Even though you may not expose the plastic container to high temperatures (like in a hot car, for example), you can’t know if the plastic object had been stored in a hot warehouse or shipped in a hot vehicle. This is especially true for single-use plastic bottled water.

It’s well known that BPA and phthalates, as well as chemicals similar to them, leach into water from single-use plastic bottles. Both are known endocrine disruptors. They disrupt hormonal balance leading to developmental and reproductive abnormalities, especially in small amounts.

BPA and phthalates are commonly used in rigid or soft plastic containers, respectively. Both of these chemicals (plus others similar to them or in the same chemical family) are known to migrate into food or drink, especially at high temperatures, with repeated use, or if they’re old. Again, you can’t know how long—or where—they’ve been stored.

It’s not just single-use plastics that are the problem, though. A 2022 study looking at leachates from reusable plastic bottles found many unknown chemicals like the 2021 study discussed earlier.

But possibly the worst aspect of plastics—with widespread adverse effects—is that they break down into microplastics. Quadrillions (a thousand trillion) of them already exist in our air, food, and drink; you and I ingest millions of them every day.

Many of them become permanently lodged in our blood vessels and major organs.

We’ve only begun to scratch the surface on how microplastics are impacting human health. Groundbreaking research from March 2024 shows that microplastic ingestion and inhalation significantly increases your risk of cardiovascular disease and stroke.  

Personally, this is all I need to know to conclude that plastic—a solid fossil fuel—is infinitely worse than stainless steel.

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Deeper dive: let’s look at the whole life cycle of stainless steel to see if it’s “sustainable”

In order to look at which material is “better” on the whole, we have to take a look at the life cycle assessment for each.

So first, what is a life cycle assessment?

A life cycle assessment (LCA) is a quantitative study of a product, process, or service that includes all the resources involved in making it. 

It’s like an accounting ledger or spreadsheet that tallies all the inputs (such as water and energy) needed for its production, use, and disposal. This type of LCA is called cradle to grave.

By contrast, a cradle to cradle LCA looks at a product, process, or service from the point of view of its sustainability on an even more holistic level. In the interest of creating a circular economy where all waste products are reused, repurposed, or recycled, a cradle to cradle LCA is the gold standard when comparing two or more products, processes, or services in terms of their sustainability.

These two general categories of product assessments may also evaluate products for their effects on the environment and on human health. 

There is a large body of computer programs available to do so. Some have free trials that you may want to take advantage of when doing your own research into products. You can start by doing a search on LCA online tools. Cross-comparing two or more LCA tools on the same product may be more enlightening—or, at least, confirming—than running the numbers using only one tool.

There are vast datasets accompanying the programs that provide the statistics used by the algorithms in their assessments. For example, the price of electricity (either renewable or nonrenewable) in numerous places around the world, or the amount of water needed to grow a pound of cotton fiber in various countries is listed. As an LCA analyst, you select the types of statistics you want your chosen LCA software to use in its number crunching.

For this article, I sought out cradle to cradle LCAs if I could find them. But unfortunately, I didn’t… Cradle to cradle LCAs are expensive, time-consuming projects that many companies can’t afford. Or, companies don’t see the value in conducting them because their customers express no interest in their results. (You and I have gotta change this!) 

As a result, the assessments completed in the scientific studies below differed greatly from each other. 

This means it was difficult to draw one, specific conclusion from them.  

That said, I did discover many interesting LCA-based studies to assess the health and environmental impacts of plastic vs. stainless steel, and we can still get a lot of great information from them. I summarize a few here.

Stainless steel vs. plastic: LCA case studies

One of the important things to remember about stainless steel is that there are several steps involved in manufacturing it. Each one has its own carbon footprint. Additionally, there are other elements—such as chromium and nickel—used in the final product. I discovered that the carbon emissions associated with those metals may be even higher than steel’s. The take home message here is when comparing LCAs, make sure you’re comparing the exact same things. This can get tricky.

According to the nonprofit Rocky Mountain Institute, the steel industry is one of the largest emitters of carbon dioxide of all industries, contributing 6%–7% of global greenhouse gas emissions. Understandably, this industry gets criticized by environmentalists and concerned citizens for its emissions and high-energy usage. In response, the industry is beginning to switch to low-carbon methods as I describe below. 

Unable to locate a cradle to cradle LCA for steel or plastic, I found several analyses comparing the environmental and health effects of certain kinds of stainless steel products vs. plastic products. 

It’s interesting to note that they all come to the same conclusion, thereby informing my final conclusion about the pros and cons of stainless steel vs. plastic (see below).

Stainless steel vs. plastic surgical instruments

When viewed for repeated usage, reusable stainless steel scissors are better than disposable stainless steel or disposable plastic scissors. Here’s a graph that summarizes the results. I chose this particular graphic because it lists many environmental parameters that a robust LCA includes (not all do). 

Unfortunately, this LCA lists only one human category: “human toxicity.” This is vague. Some LCAs include human carcinogenicity as a separate metric. Potential for endocrine disruption would be a helpful metric, but unfortunately, I have never seen it in any LCA tool.

Winner: reusable stainless steel

Stainless steel vs. plastic tableware in aviation catering

This study included many different plastics such as polystyrene, polypropylene, and polylactic acid (PLA), as well as bamboo and stainless steel. After only 29 times of use, the carbon footprint of stainless steel dropped below that of all other cutlery, including a 68.1% drop compared to polystyrene. 

Winner: stainless steel

Stainless steel vs. acrylic specula in gynecological exams

An LCA was conducted in a university health clinic. Based on 5,000 pelvic exams, a reusable stainless steel speculum was better than an acrylic speculum in terms of global warming, acidification, respiratory effects, smog, and fossil fuel depletion. The acrylic speculum scored better in the ozone depletion category. Both scored equally well in the carcinogenic, non-carcinogenic, ecotoxicity, and eutrophication categories. 

Winner: depends on the category

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Buyer beware: LCAs can be misused by industry to greenwash

Industries that want to portray their products in the most favorable light possible can easily manipulate an LCA’s parameters to exclude areas in which their product fails. For instance, in the case of ocean plastic pollution, plastics companies may exclude marine effects, or not consider their product’s disposal (end-of-life) in the calculation. It’s well known that plastic lasts practically forever, degrading to microplastics that we eat and breathe as they leach in a landfill, contaminate groundwater, and emit air toxins when incinerated. So, a plastics company would be disinclined to include end-of-life concerns in an LCA. 

To avoid being misinformed, you should always consider multiple LCAs based on the same system parameters and not developed by industry when assessing a product’s impacts. 

The potential misuse of an LCA has serious implications. Since LCAs are often relied upon by governments to set policy, decision makers must be sure that LCAs have been conducted by an independent party with no financial ties to the industry. 

For example, if a government was considering how to regulate plastic pollution, its officials could be given an LCA generated by the plastics industry that concluded reducing or eliminating plastic could have negative environmental consequences. Or, unbelievably, that LCA could even be used to justify more virgin plastic production! (Both statements are based on real LCAs.)

Stainless steel production has a high carbon footprint… How can they fix that?

Currently, there are only a handful (8%) of steel companies producing low-carbon (“green”) steel using the most promising technology to date, which is known as hydrogen-based direction reduction (HDR). 

(This is not the same as green hydrogen, a potential renewable energy source when it’s sourced from water, not methane gas.)

In a 2019 report by the Rocky Mountain Institute on HDR, manufacturing primary (i.e., made from iron ore) steel with hydrogen has the same carbon footprint as the most common way to produce steel: the blast furnace method. So how could HDR be called green?

The carbon footprint of the traditional method to manufacture steel includes using high-carbon coal (in the form of coke) as the substance needed to separate purified iron from iron ore in an energy-intensive process. HDR relies on carbon-free hydrogen to do the same step. 

However, although the carbon footprint of HDR for that part of the process is lower, there are carbon emissions associated with other steps in the steel-making process using hydrogen. The final tally of carbon emissions is roughly the same for both methods right now.  

The upshot of this fact is that manufacturing steel without coal doesn’t generate more carbon emissions than the traditional process that relies on coal. When the power supplied to make HDR steel is from renewable sources, the carbon footprint would be significantly lower.  

In fact, considering the sources of grid power in the United States, switching to HDR steel manufacture is predicted to result in an immediate 20% reduction in carbon emissions. Additional good news is that since the price of electricity generated from renewable energy is the same or even less than that from coal-fired power plants, green steel represents a significant climate and economic win.

So, you may be wondering, why hasn’t the entire steel industry switched to green steel by now?

In order to make that a reality, major market, regulatory, and financial interventions must be put into place. For starters, the blast furnaces used to make conventional steel must be converted. This is a costly undertaking that adds to the R&D dollars already spent to develop the HDR technology.

Some of the ways to make the transition smoother include:

• Green steel industries must market their product to make it shine to attract eco-conscious consumers, thereby creating a supply-demand dynamic that will eventually lower the price of HDR steel.
• A carbon tax (or something similar like import tariffs) to reduce the cost advantage of high-carbon steel over green steel must be introduced. 
• Investors and stakeholders must pressure traditional steel companies to account for their high carbon footprint and seek ways to transition to low-carbon technologies. 

Stainless steel vs. plastic: pros 

How do these two materials stack up? Here’s a chart that weighs the advantages of stainless steel against the only good point of plastic that I can think of.

Pros

Stainless steel	Plastic
No chemical additives	Lightweight
Infinitely recyclable
Withstands heat
85%+ is recycled
Negligible leaching of nickel and chromium, if any
Generally non-reactive to foods, beverages
Indestructible
Green steel made with renewable energy is low-carbon

Stainless steel vs. plastic: cons

What are the downsides to these two materials? Check out a table that sets the disadvantages of stainless steel against those of plastic.

Cons

Stainless steel	Plastic
Traditional method produces high carbon emissions	Leaches toxic chemicals into foods & beverages when heated or not
Traditional method uses coal, a non-renewable resource	Produced from a non-renewable resource
Energy-intensive	Can’t be recycled more than once or twice
Requires mineral mining (unless recycled material is used)	Most plastic is not recycled at all (<5%)
	Contributes to ocean pollution
	Forms toxic microplastics
	Toxic to aquatic organisms
	Releases carcinogens (dioxins, furans) when incinerated

Key takeaways: stainless steel vs. plastic

After carefully considering the pros and cons of stainless steel vs. plastic, I’m left with only one conclusion: stainless steel produced by the HDR method is far superior in all the ways that matter. 

I’ve analyzed case studies of life cycle assessments conducted by independent researchers of both materials. All three conclude stainless steel is less harmful to the environment and human health than plastic.

Currently, the major negative for stainless steel is its huge carbon footprint. Fortunately, there is promising research going on to lower it significantly. Some of these advances are entering the mainstream already.

On the other hand, I’m hard pressed to find anything that makes plastic shine above stainless steel. When I think of all its negatives—especially that it’s indestructible and causes severe environmental and human health damage when it breaks up into microplastics—I find that the world would be a much better and healthier place without it.