As Houston makes plans to expand its port, residents near the Houston Ship Channel are bracing themselves. The predominantly Hispanic and black East Houston neighborhoods bordering the port are already exposed to some of the worst air pollution in the country, and not without consequence. A recent survey, conducted by the Healthy Port Communities Coalition, found that residents of five neighborhoods surrounding the Ship Channel suffer from higher rates of cancer and respiratory illnesses than average Texans.

The findings reinforce what people in these neighborhoods have known or suspected for many years, but they also come at a critical time for the Port of Houston. Along with other port cities, Houston is preparing for the expansion of the Panama Canal, slated to be complete by 2015. Record-setting freight activity is already underway at the Port of Houston.

Los Angeles, Miami and Houston are among the many cities investing millions in huge dredging projects to make their channels deep enough for the “post-Panamax” ships that will soon sail into their harbors. But with more (and much larger) vessels come greater diesel emissions, and Ship Channel residents worry their hard-hit communities will only suffer more with increased air pollution. Diesel exhaust has been linked to respiratory and heart disease, and is a known carcinogen.

According to the report, which analyzed self-reported health data from nearly 400 people in Houston’s East End, Fifth Ward, Denver Harbor, Manchester and Pasadena neighborhoods, adults in those areas suffered from asthma and other respiratory diseases at more than twice the rate of other Texans. And while 3.69 percent of Texan adults have been diagnosed with cancer, the survey puts the cancer rate in the Ship Channel at 5.61 percent.

Last month, the World Health Organization officially added air pollution to the list of known carcinogens. According to the organization, air pollution was responsible for more than 220,000 lung cancer deaths worldwide in 2010, and also increases the risk of bladder cancer. Scientists have long known that air pollution can lead to or exacerbate heart disease and respiratory diseases such as asthma.

But because some pollutants have unclear and wide-ranging effects on human health, and because diseases like cancer can have a variety of causes, it’s difficult to trace specific medical conditions to particular pollutants. In Houston, people aren’t just exposed to one pollutant, but to a variety of potentially toxic emissions from a vast industrial complex that includes refineries and chemical plants. Despite recurring health problems, more than half of those surveyed said they didn’t have health insurance.

Elena Craft, a scientist with the Environmental Defense Fund of Texas, says although the study can’t pinpoint the sources of East Houston residents’ medical conditions, it sheds light on an alarming concentration of illness that requires immediate attention.

“We know there’s an increased risk [in the Ship Channel], but to pinpoint is more difficult, especially on self-reported data,” Craft says. “It would take further investigation to get a better handle on the extent of the issue and where there might be more serious problems.”

Craft, who was not involved with the study, says she hopes it will empower area residents to demand change. She says many sources contribute to Houston’s air problem, not just the port, but that residents could pressure the port authority to actually start addressing emissions, the way Southern California homeowners did in the early 2000s.

In 2006, the ports of Los Angeles and Long Beach together adopted a comprehensive clean air action plan to drastically reduce emissions and encourage the development of clean technologies. It was an unprecedented victory for both area residents and environmentalists, especially since the San Pedro Harbor was Southern California’s single biggest source of air pollution and Los Angeles has long been the nation’s smoggiest city.

Through cutting vessel emissions, replacing old diesel trucks with new or retrofitted trucks, and investing in initiatives like electrified docks that ships can plug into, the ports have exceeded their emissions reduction goals for some pollutants. By 2012, the two ports had cut their diesel particulate matter emissions by 77 percent (eliminating 645 tons) from 2005 levels, sulfur oxides by 88 percent (4,675 tons), and nitrogen oxides by 56 percent (9,154 tons). When seven terminal operators violated San Pedro Bay’s new diesel emissions standards, they each paid $1 million in cleanup costs as part of a settlement reached in 2011.

It’d be a rather monumental stretch to imagine the Port of Houston Authority adopting measures as aggressive as Los Angeles’, not to mention actually enforcing them to the point of fining companies for environmental violations. But in its report, the coalition does make some recommendations that could be a good starting point for cleaning up Texas’ biggest port and most polluted major city.

First, the coalition says the port authority needs to be a leader in reducing emissions, partly by giving preference during bidding to contractors with clean practices. It also recommends setting up emissions reduction goals and installing fence-line monitors to help enforce federal air-quality standards. Houston should follow the Los Angeles-Long Beach Ports’ example, the coalition suggests, by phasing out old diesel trucks and introducing electricity to ports so ships can conserve diesel fuel while docked.

The Port of Houston Authority came under scrutiny last year after a critical report by the Texas Sunset Advisory Commission. During the last session, the Texas Legislature passed a bill that set term limits for board commissioners and fired four of the seven commissioners. Two of the remaining three members had recently been appointed, so only one of the commissioners currently on the board has been there for more than a year.

Fresh blood could be a good sign, but Craft says so much change makes it to hard to predict what the board might do. The body says it values environmental stewardship and that it has taken measures to clean up the air. But Houston remains in non-attainment of federal air quality standards, and environmentalists say the port area has a long way to go.

“I think there’s all kinds of questions that this report can raise to the port authority,” Craft says. “If I were the port authority I would be incredibly concerned.”