New Zealand mesothelioma specialist Dr Richard Sullivan believed she was exposed around the age of 10 "during regular visits to building sites with her electrician father or during contact with fibres on his hair and clothes on his return home".
In its "Likely decision advice report" to Ms Trevarthen on December 21 last year, ACC said cover would probably be declined.
In his decision to the ACC claims department, the company's lead occupational health adviser John Monigatti said 95 per cent of mesothelioma cases were caused by asbestos. Because Ms Trevarthen worked in a non-asbestos environment as a sales representative, he said she may be among the "small percentage of people in whom mesothelioma arises without apparent cause".
Mr Robertson is furious ACC made its decision without talking to her specialist.
ACC spokeswoman Stephanie Melville said all aspects would be considered before a final decision was made.
"It hasn't been declined yet, the final cover decision is still pending while we investigate fully," she said.
Mr Robertson believed ACC's "hands were tied" by outdated legislation. He wanted an overhaul of the 2001 policy to keep up with medical advances - including new knowledge that minimal exposure to asbestos can do harm.
Ms Trevarthen is into her third round of Government-funded chemotherapy. She has three more rounds of chemo before she is faced with a $65,000 round of Avastin to prolong her life. The couple are also planning other life-extending treatments that total $200,000 - none of the treatments are funded.
"If Deanna's dad had mesothelioma ACC would have paid out within four days," Mr Robertson said. "But Dee, exposed to the same stuff, gets nothing except $200,000 of medical bills and a battle that currently experts say she can't win."
To help Deanna visit: givealittle.co.nz/cause/deesday