Dishwashers are one of the more difficult purchases when planning your non-toxic home because they use many different materials and it’s difficult to get manufacturers or retail sellers to disclose those materials. Many sales representatives simply don’t know what’s used to make their products.
When I purchased my dishwasher a few years ago I was focused on finding models that didn’t use PCV in the racks. Recently, a new material of concern, bitumen, has been a popular topic in Toxic-Free Q&A.
Bitumen in Dishwashers
According to Wikipedia, bitumen, also known as asphalt, is a sticky, black, liquid or semi-solid form of petroleum. It’s widely used in dishwashers as a sound-deadening insulation. Some consumers complain of a tar smell from newly installed units.
But, just how dangerous is bitumen when used in these conditions? Research on the toxicity of asphalt focuses on the fumes that workers are exposed to in the pavement and roofing industries. It’s less clear how much it off-gasses once cured. Miele, a manufacturer of high-end dishwashers, claims that the bitumen is fully encapsulated and will never emit any vapor or fumes of any kind. The bottom line is more testing needs to be done to better understand the toxicity of bitumen in this application.
Some models use more bitumen than others depending on the type of tub. Base on the information I received from 7 manufacturers, dishwashers with stainless steel tubs generally use bitumen in the insulation on all sides of the tub. Dishwashers with plastic tubs generally only use bitumen in the door panel or lid. So, is it better to have less bitumen with a plastic tub or more bitumen with a stainless steel tub? Again, it’s hard to say without better understanding just how dangerous bitumen is under each condition.
Here’s where it gets even trickier. The one model I found that does not use bitumen uses other materials for sound-deadening insulation. The GE model GDF630PSMSS uses an insulation blanket and insulation mastic. The manufacturer was unable to tell me the materials used in those items but according to Wikipedia, among the commonly used materials in insulation blankets are PTFE laminates. That’s right, PTFE, otherwise known as Teflon. Mastics, like coatings and paints, have a range of VOC levels depending on the formula, so it is impossible to assess the toxicity without more information.
A further complicating factor is that it’s difficult to rely on information gathered from manufacturers. Some models that readers posted as free of bitumen are ones that I found to contain bitumen, but with a lower amount than other models. Again, I don’t believe this misleading information is intentional but more a lack of understanding by company employees. Nonetheless, it’s hard to know exactly what you are getting.
Here’s how 7 dishwasher manufacturers reported their use of bitumen.
Bosch: All models are made with bitumen.
Fisher & Paykel: Sides are insulated with cotton fiber and bitumen is used on the top of the lid.
GE: All models are made with bitumen with the exception of model #GDF630PSMSS which uses an insulation blanket and insulation mastic.
KitchenAid: All have bitumen in some degree. Models with stainless steel tubs use bitumen on all side. Models with plastic tubs only use bitumen in the door panel.
Maytag: All have bitumen in some degree. Models with stainless steel tubs use bitumen on all side. Models with plastic tubs only use bitumen in the door panel.
Miele: All models are made with bitumen, but it is fully encapsulated and will never emit any vapor or fumes of any kind.
Whirlpool: All have bitumen in some degree. Models with stainless steel tubs use bitumen on all side. Models with plastic tubs only use bitumen in the door panel.
Plastics in Dishwashers
This is actually some good news. Plastic components inside of new dishwashers, which can include tubs, racks, silverware baskets and spraying arms, are now being made with safer plastics. PVC used to be a commonly used material in racks but fortunately, most are now made of nylon. Plastic tubs, silverware baskets and spraying arms are usually made with polypropylene, which does not contain BPA or phthalates. It’s worth verifying, before you purchase a specific model, that the parts are made with these safer plastics.
Let’s continue to gather information on dishwashers. What has been your experience with new dishwasher purchases? Are there detectable odors after installation and for how long? Have you found a model that is free of bitumen? Keep me posted!