Things have not been going well for Altria (MO 0.61%), to say the least. The tobacco stock is down 30% in just two years, well short of the S&P 500's returns of 23% during that time. And the concern for Altria investors today is that a turnaround may not be in the cards for 2020.

The danger is that shares of Altira may continue to plummet this year. The big reason behind the risk: vaping.

Altria's latest writedown may not be its last

Vaping-related illnesses are weighing down the prospects of what was once supposed to be a source of high growth for cigarette maker Altria. With the Centers for Disease Control and Prevention now saying there are over 2,700 cases where people have suffered lung injuries as a result of vaping products, consumers are on high alert, and vape sales are struggling

It's no surprise that Altria took a $4.5 billion writedown in October on its investment in JUUL Labs given the industry's challenges. What may have surprised investors is that in January, Altria took another $4.1 billion hit. That's more than two-thirds of its original $12.8 billion investment in Juul now off its books. 

A vape pen

Image source: Getty Images.

As bad as things are, they could continue to get worse for Altria. The Food and Drug Administration (FDA) is reviewing Juul and other e-cigarette products in May. The concern for Altria is that health officials may take Juul products off the market completely. And according to former FDA Commissioner David Kessler, it's not just a possibility, but a likelihood given how prevalent teen vaping has been.

Without proof that its products help users quit smoking, Juul will have a hard time proving that its products offer a "net public health benefit," which is what the FDA will be looking for in determining whether it will approve the products. If the FDA decides to ban Juul products, investors can expect to see Altria making yet another writedown of its investment.

Its investment in Cronos may not be any safer

Altria has not written down its $1.8 billion investment in cannabis producer Cronos Group (CRON -4.82%), but that too may be an inevitability. The marijuana stock is down 67% over the past 12 months, which is in line with the 60% decline that the broader Horizons Marijuana Life Sciences ETF experienced during that time. Cronos was banking on the popularity of vaping to give it an edge over its peers, and now that remains a big question mark.

While Cronos is based in Canada and can still sell vapes there, that could change as well. Canadian governments are starting to take a closer look at vaping products, and on April 1, Nova Scotia will become the first province to ban flavored e-cigarettes. 

Not only has the potential for vaping been affected, but the cannabis industry as a whole in Canada has struggled. Research company BDS Analytics cut its forecast for the Canadian cannabis market last year, now expecting sales to reach $5.2 billion by 2024. Previously, the company forecasted the market to be worth $5.9 billion by 2022. With the cannabis industry struggling, Cronos may be another potential writedown for Altria in the future. 

Implications for Altria go beyond just writedowns

As bad as possible writedowns are for Altria, the problem goes much deeper for the stock. Vaping and cannabis were supposed to be high-growth areas that could inject a lot more revenue to the company's top line. Altria's revenue over the past four years has stayed within a narrow range of $19.3 billion and $19.8 billion; there just hasn't been much growth at all.

Without stronger growth prospects for the future, the stock may face some challenges in 2020 in winning over investors. Although it offers a dividend yield of 7.3%, investors are clearly apprehensive about investing in the stock as it trades at a forward price-to-earnings multiple of less than 10, which is a very modest multiple. 

There's a lot of risk for investors who buy shares of Altria today, and until that changes, the stock's valuation could continue to go lower, especially as concerns surrounding vapes and the cannabis industry weigh on the minds of investors.