It’s one of the most frequent complaints among California tenants, but until 2016  there was little they could do about potentially hazardous mold in their units.

Since 2016, state law considers mold a condition of substandard housing.

That means for the first time, renters can report problems to their city or county code enforcement which can demand repairs and fine landlords who don’t comply.

Mold is also linked to asthma and other respiratory problems.

Code enforcement officers are already addressing mold complaints under the new law.

California Sen. Holly Mitchell (Los Angeles–D) authored the bill to amend the Health and Human Safety Code that regulates housing conditions. The California Association of Code Enforcement Officers and Oakland-based Regional Asthma Management and Prevention co-sponsored it.

They point to a 2011 statement from the California Department of Public Health that says visible mold and mold odor in dwellings increases the risk of respiratory disease.

In 2001, the department began studying how much mold poses a risk. After four years of research, health officials told the legislature there is no “sound science” for establishing safety limits for mold in dwellings, but that there is consensus among medical professionals that its presence causes asthma, allergies and respiratory infections.

The lack of any formal guidelines on how much mold is too much is part of why regulation hasn’t existed until now, and why tenants have a hard time arguing for damages in court.

The health and safety code already considered “dampness of habitable rooms” a substandard housing condition. This year’s amendment adds “visible mold growth, as determined by a health officer or a code enforcement officer, excluding the presence of mold that is minor and found on surfaces that can accumulate moisture as part of their properly functioning and intended use.”